Another excellent argument was made by the Sautrantika, and is here elucidated:
“The Yogacara argues that though the object is identical with its cognition and is nothing but a mode of consciousness, yet it is illusorily presented as distinct from, and external to, the cognition. The object whichis a mere form of cognition (jfJanasvarupa) appears to us as if it were an external entity owing to an illusion. The duality of subject (grahaka) and object (grahya) is an illusory appearance. Cognition alone is real. What is really an internal cognition appears to be an external object. The Sautrantika urges that if there are no external objects at all, we can never assert that internal cognitions appear to be external objects. The illusory appearance of externality presupposes the real knowledge of externality somewhere. If we were completely ignorant of the external world, we could never speak of the illusory appearance of externality. No sensible person would say : “ Vasubandhu looks like the son of a barren mother.’ * The sense of objectivity can never be derived from mere modes of consciousness.”
“…The Sautrantika advances the following formal argument to prove the existence of external objects. Those things which appear at times, while another thing is uniformly present, must depend upon something else. The series of self-cognitions (alayavijnana) is uniformly present. But object-cognitions (pravrttivijflana) appear occasionally. Therefore they must depend on something other than the series of self-cognitions. They are caused by external objects which are independent of all cognitions… The Yogacara holds that the occasional appearance of object-cognitions (pravrttivijnana) is not due to external objects, but to the maturation of subconscious impressions (vasanaparipaka) within the stream of consciousness itself. The variety of object-cognitions or sensations is due to the variety of subconscious impressions (vasana) which appear and disappear in a beginningless series of nescience. (Dbject-cognitions break in upon the field of consciousness owing to the revival of subconscious impressions in the same psychic continuum. They are not imposed from without but are evolved from within. Subconscious impressions are awakened by those antecedent mental states with which they were associated in the past, and are raised to the level of consciousness. The revival of subconscious impressions is responsible for the emergence of object-cognitions or sensations. They cannot be traced to external objects. Sensations are not “ given They are creations of the mind. The Yogacara advocates unadulterated subjectivism or mentalism. But the Sautrantika contends that if all subconscious impressions have a tendency to rise above the threshold of consciousness, why they should remain at all in the subconscious level as latent predispositions is unintelligible. Then, again, why a particular antecendent mental state awakens a subconscious impression and brings it to the level of consciousness is a mystery. It may be awakened by all the antecedent mental states in the same psychic continuum, because they all equally belong to the same continuum. If all the antecedent mental states cannot awaken a subconscious impression, a single antecedent mental state cannot awaken it either. Then, again, it is absurd to suppose that all previous mental states awaken a subconscious impression, and modify a particular psychosis. Thus subconscious impressions can never account for object-cognitions or sensations. Hence the Sautrantika concludes that we must admit the reality of external objects capable of exciting the sensations of sound, touch, colour, taste, smell, and feelings of pleasure and pain occasionally.” -Indian Realism, Jadunath Sinha, p 38-42
The Jaina adds:
"Mallisena’s Criticism of the Yogacara Idealism
(1) Cognition is an act (kriya). It is an act of knowing an object. It must have an object. The act of cognition is directed to an object. It is an act by which an object is known. An objectless cognition is impossible.* An illusion is not absolutely objectless. The illusory perception of hairs in the sky presupposes perception of real hairs at some other time and place. Dreams also are recollections of objects actually perceived in the past. Neither illusions nor dreams are absolutely objectless.* The object which is apprehended by a cognition is external. The cognition of externality cannot be said to be illusory, since an illusion consists in the apprehension of an object actually perceived in the past and attributed to another object perceived at present owing to defects of the sense-organs and the like. An illusion presupposes perception of an external object at some other time and place. It is not without a substratum in external objects. Therefore it cannot disprove the existence of external objects.* (2) An external object has practical efficiency ; it produces effects and fulfils our needs. So the cognition of an external object cannot be said to be illusory. If it is supposed to be illusory in spite of its practical efficiency, the distinction between valid perception and illusory perception will be abolished, and the satisfaction of a person eating real sweetmeat will be the same as that of a person who dreams of eating sweetmeat. But real sweetmeat is never the same as imaginary sweetmeat. There is a distinction between real things and imaginary things. Real things serve our practical purposes. But imaginary things have absolutely no practical use. Therefore the existence of external objects is proved by their pragmatic value. … the difference between the object and its cognition is distinctly perceived. Perception proves their difference. Inference cannot disprove it. The evidence of inference is of no value against the evidence of perception. Perception decides the issue when there is a conflict between perception and inference. … Everybody perceives an external object. The universal experience of mankind bears testimony to its existence. To deny the reality of external objects is to fly in the face of it. -ibid. p 65-66
The Samkhya have some problems with idealism, too:
“Aniruddha sets forth the following arguments against subjective idealism ; — Firstly, the world is not made up of mere ideas because, if it were so, an external object, e.g. a jar, would be perceived as I am a jar ”, and not as “ this is a jar ”. But, as a matter of fact, an external object is always perceived as “ this ” and not as “ I ”. It is perceived as of the nature of not-self as distinguished from the self. The self and the not-self are diametrically opposed to each other. Secondly, the difference in the perceptions of objects cannot be due to the distinctive peculiarities of the subconscious impressions (vasanaviSesa) ; for if there is no external reality at all, there can be no subconscious impressions of jars and the like, and so there can be no such distinctive peculiarities in subconscious impressions. Then, again, we may ask what is the cause of the socalled subconscious impression (vasana). It is either another subconscious impression or an impression left by a previous perception of something external (bahyavasana). If the former, there will be no determining condition of the perception of different objects, and there will be perception of everything at all times. If the latter, there does exist something other than cognitions, and this very object is an external reality.” -ibid p 77-78
As does the very well known Yoga school of Patanjali:
…The external reality is presented to consciousness as “this” by its own presentative power. It is the given. It is an object of perception which is valid. The Yogacaras deny the reality of the external world on the strength of imagination which is invalid. Imagination cannot override the authority of perception. The external object is real and independent of cognition ; it is presented to the cognition by its own power The Yogacaras first suppose that external objects are presented to consciousness because they are mere construction of imagination ; then they deny the reality of the external world on the strength of such an imaginary hypothesis. So they cannot be trusted. Vijnianabhiksu explains Vyasa’s criticism thus: All perceptible objects are presented to consciousness through their intercourse with the sense-organs by their own power. They are perceived by their own power of perceptibility. They are objects of direct perception. They cannot be likened to objects of dream-cognitions which owe their existence to some disorders of the body or the mind. The objects of perception are not contradicted like those of dream-cognitions. So the existence of external objects apprehended by valid perception can never be denied on the strength of invalid dream-cognitions. The Yogacaras who deny the reality of the external world cannot be trusted, since, on their own hypothesis, their ideas have no counterparts in reality, and their words are not expressions of true ideas and do not denote real objects. Thus by denying the reality of the external world the Yogacaras deny the truth of their own statements." ibid. p 83-84
“May Sinclair states the position of the realist thus : “ No act of mere knowing, even if it were absolute — and knowing is purely relative to the known and the knower — no act of knowing could confer reality upon its object. Things are not there because we know them ; we know them because they are there.“ In no sense are things there because we perceive them ; we perceive them because they are there and they owe nothing to our perceiving.” * Thus an object is known by an act of cognition, not because it is identical with the cognition, but is different from it. (2) Vacaspati argues that knowability (vedyatva) of an object by an act of cognition is not pervaded by identity between the object and the cognition, and therefore it cannot negate the difference between them. An object is not known by a cognition because it is identical with the cognition. Therefore its knowability cannot disprove its difference from the cognition. In fact, knowledge of an object by a cognition presupposes a difference between them. May Sinclair states the realist’s position thus : “ If a thing is known, ipso facto it is something more than the act, or state of knowing. Idealism assumes that this act or state is simpler than it really is. Knowing involves at least two terms and a relation, whether you take the subject and object as your terms and consciousness as your relation, or consciousness and the object of consciousness, when your relation will be an unknown x. In either case the object will stand on its own feet as a separate and independent entity, which is all that realism wants.” " According to realists, the process of knowledge always implies that the mind is confronted with an object, and always implies that we are never under any conceivable circumstances identical with that object. Even when we apprehend our own experiences, the process of apprehension cannot be identical with the experience which is apprehended.” Therefore the cognitive relation is not the same as identity. Vacaspati points out that the reasons advanced by the Yogacara for the denial of external reality, viz. knowability (vedyatva) and invariably simultaneous perception (sahopalambha) are not conclusive, since the application of the method of difference here is doubtful, or rather impossible.” -ibid p 85-86
"…both the arguments of the Yogacara are fallacious. Neither knowability of the object (vedyatva) nor invariably simultaneous perception of the object and the act of knowledge (sahopalambha) can prove the identity of the object with its cognition. (4) Further, the power of perception cannot be done away with by mere imagination. The certainty of perception which gives us a direct and immediate knowledge of external objects can never be rejected on the strength of imagination or logical abstraction. (5) Further, externality (bahyatva) and extension (sthulatva), the attributes of the material objects and phenomena which are apprehended by cognitions, can never exist in them. … Further, Patanjali says : “ Though the object remains the same, the ideas about it may be different. So their ways of being are different. ’’ Vyasa explains the above argument thus : One and the same object is common to many minds. It is not the “ private property ” of any individual mind. It is the “ public property ” of all minds. It is the common object ofobservation of all minds ; it is equally accessible to them all. So it cannot be regarded as creation of imagination. It is neither imagined by one mind nor imagined by many minds. But it exists in itself and for itself independently of all minds. The object has extra-mental existence. It is not the subjective creation of fancy Even though the object remains the same it excites different feelings in different persons. It excites the feeling of pleasure on account of merit (dharma). It excites the feeling of pain on account of demerit (adharma). It excites the feeling of delusion on account of nescience (avidya). It excites the feeling of indifference on account of right knowledge (samyak darsana). Since one and the same object excites different feelings in different persons, it cannot be regarded as creation of anybody’s imagination because one’s imaginary ideas cannot produce similar ideas in other minds. Thus the object exists in itself independent of all minds. The object and its cognition are different from each other ; the object is apprehended (grahya) and the cognition is the apprehending mental mode (grahana) ; both of them are real and existent and can never be confused with each other. Similarly Vijfianabhiksu says that both the object and the mind are said to be self-existent (svatantra), since they are independent of each other. Vacaspati argues that of two things, if one remains the same and the other differs, they must be absolutely different from each other. The same object is perceived by Caitra, Devadatta, Visnumitra and Maitra. Here though the object remains the same, the ideas of different persons differ from one another. So the object must be different from ideas. The identity of the object is ascertained by different persons perceiving it by comparing notes, though their ideas of the same object differ from each other. " -ibid p 89-90
“Bhojadeva argues that the object cannot be a creation of the mind, since the same object excites different feelings in different minds. If the object were the creation of an individual mind, it would appear to consciousness as uniform, and it would cease to exist when that mind would attend to some other object, and it would never be perceived by any other mind. But, as a matter of fact, an object is observed by many minds, and so it cannot be regarded as the product of an individual mind. If it were created by many minds at the same time, it would differ from the creation of an individual mind.” -ibid. p 92-93
“The Yoga Criticism of a Type of Buddhist Realism Some Buddhists hold that the objects are real and external to minds, but they come into existence along with our cognitions, since they are experienced like pleasure and pain. They are not subjective idealists. The external objects, according to them, have no existence either in the past or in the future, but have only a momentary existence in the present moment. They come into existence when we perceive them, and they cease to exist when we cease to perceive them. Dr. Das Gupta puts it thus : “ The moment I have an idea of a thing, the thing rises into existence and may be said to exist only for that moment and as soon as the idea disappears the object also vanishes, for when it cannot be presented to me in the form of ideas it can be said to exist in no sense.” Vacaspati explains the above Buddhist position thus : Let the object be different from its cognition. Still the object being unintelligent cannot be apprehended without a cognition. It is manifested by a cognition. So it cannot be said to exist at a time when it is not the object of immediate knowledge. Vyasa urges that this conception of an object coming into existence with a cognition contradicts the fact that the object is common to all persons, and thus denies the existence of the object in the past and in the future. Vacaspati says that an object is certainly common to all minds. It continues to be apprehended by persons for a succession of many moments though it is changing in its nature. This clearly shows that it does not come into being along with its apprehending cognition. If the object comes into being with a cognition, its appearance and disappearance must depend upon cognitions. But this is not the case. Further, if an object owed its existence to a cognition, it would never be presented to consciousness as “ this ” (idam). But, as a matter of fact, an object is always perceived as “ this ” ; and it cannot, therefore, owe its existence to a cognition. Patanjali says : “ An object does not depend on a particular mind ; for what will happen to it when it is not apprehended by that mind ? ” Vyasa explains the aphorism thus : If the object depends on a particular mind, what will be the fate of the object when that mind will attend to some other object, or restrain all its functions, since at that time it will neither be apprehended by that mind nor by any other mind. So it will cease to exist at that time. And if it thus ceases to exist, how can it again come into existence when the attention of the individual is again directed towards it * Further, all parts of an object are not apprehended by the mind at the same time. So those parts which are not apprehended would not exist. Thus when the front side of an object is apprehended, its back side which is not apprehended at the time cannot be said to exist. And if the back side does not exist, the front side also may as well be said not to exist because they are held to be coexistent with each other. Thus the whole object would be regarded as nonexistent. Hence Vyasa concludes that the external reality is independent of all minds, and is the common object of observation of all persons; there are different minds in different persons ; and all the experiences of the self arise from the relation of the mind with the external world.” -ibid p 95-96
A Note on Science:
One might note that if the above criticized type of perception, namely the Yogacara position things only exist when we are aware of them, was, in reality, how things are, our cars wouldn’t work, because we only observe the front while driving, and so the rear tires would cease to exist! In fact, all the tires would cease to exist, as would the outside of the car! Ditto for everything else. Almost nothing would work, from science experiments to cooking dinner. Further, the scientist doing experiments on things that cannot be seen with the naked eye would be doing no experiment at all! There would be nothing in the space that they cannot see. Since quantum particles, like electrons, cannot be seen by the naked eye, nor by even a magnified scope of any kind, this would mean not a single quantum experiment has ever been carried out.
On the other hand, if interacting with the experiment indirectly, while not directly conscious of the particles, using inanimate instruments, and inferring that particles are doing whatever they are doing, is enough to determine that the particles are actually there, then this would mean that everything is interacting with everything, and thus that everything exists, regardless of whether or not anyone is aware of it. If the particle I cannot see is around to interact with things, even though I’m not directly aware of it, because it is interacting with inanimate matter, then all inanimate matter, everywhere, should keep all other inanimate matter in place, as well. Hence, the idea that any quantum experiment has proven that reality doesn’t exist when we are not aware of it self refutes, because we are not directly aware of quantum particles, and so if they don’t exist when we are not directly aware of them, then the experiment never happened.
This is actually known as decoherence, and is a well known fact. Yet, many flock to the interpretations of physics experiments seen in click bait headlines, and shout “Science has proven objective reality doesn’t exist!” without realizing this is a self refuting statement. In reality, a single quantum when isolated from all the outside world goes into a wave state. Once it is observed again, it collapses back into a particle.
This “observation” cannot be done by a human mind, such is impossible, because we have no way to directly image them. The “observer” is an inanimate instrument. The rest of the world and all of its quantum particles stay in their particle state because they are always “observed” by all kinds of macroscopic objects.
Really, someone seriously dropped the ball when they decided to call “interacting with a quantum particle” “observing” because this has lead to countless people thinking that consciousness is what collapses quantum particles. In reality, we are NEVER conscious of quantum particles directly, because we cannot see them, nor detect them in any way whatsoever without inanimate objects, which, themselves, must exist to do the experiment in the first place, and so on, as above.
So, while people write books called “The Quantum Enigma: Physics Encounters Consciousness,” we need to remember that, no, physics did not encounter consciousness at the quantum level, because consciousness of the quantum level of reality is completely impossible, and can only be inferred from results from the inanimate, non conscious world. For a much better explanation of the quantum world, see Rodney Brooks’s “Fields of Color.” For some more, and some amusing responses to this type of alarmist, asinine interpretation of quantum mechanics, see below:
“Quantum mechanics (QM) is supposed to be a universal theory: its domain of applicability is not restricted to the world at very small length scales. In other words, the theory is meant to describe elephants as well as electrons. While we do not, of course, need to use quantum theory to describe elephants, there are increasingly larger and more complex laboratory systems (i.e., tabletop experiments) being built that do display quantum behaviour. There are various proposals for why, in practice, we do not need to use quantum theory to describe the world at the length- and time-scales that are familiar to us as human beings. The central of these is decoherence—the idea that the interference effects that would otherwise reveal our ‘quantum-ness’ get suppressed when a system interacts with other systems around it (‘the environment’). Thus, demonstrating the quantum behaviour of a laboratory system requires the system to be isolated (to a great degree) from outside influences.” -Karen Crowther
"Of course there is not a new experiment that suggests there’s no such thing as objective reality. That would be silly. (What would we be experimenting on?) There is a long tradition in science journalism—and one must admit that the scientists themselves are fully culpable in keeping the tradition alive—of reporting on experiments that (1) verify exactly the predictions of quantum mechanics as they have been understood for decades, and (2) are nevertheless used to claim that a wholesale reimagining of our view of reality is called for. This weird situation comes about because neither journalists nor professional physicists have been taught, nor have they thought deeply about, the foundations of quantum mechanics. We therefore get situations like the present one, where an intrinsically interesting and impressive example of experimental virtuosity is saddled with a woefully misleading sales pitch. … In the experiment being discussed, branching did not occur. Rather than having an actual human friend who observes the photon polarization—which would inevitably lead to decoherence and branching, because humans are gigantic macroscopic objects who can’t help but interact with the environment around them—the “observer” in this case is just a single photon. " -Reality Remains Intact, by Sean Carroll
“A group of physicists claims to have found experimental evidence that there are no objective facts observed in quantum experiments. For some reason, they have still chosen to share the observations from their quantum experiment with the outside world.” -Dustin Lazarovici
" The MIT Technology Review article that occasions this discussion has the rather astounding title “A quantum experiment suggests there’s no such thing as objective reality”. One could be rightly puzzled about how any experiment could suggest any such thing, since the existence of “objective reality” seems to be a pre-condition for the existence of experiments in the first place. The abstract is perhaps slightly more promising: “Physicists have long suspected that quantum mechanics allows two observers to experience different, conflicting realities. Now they’ve performed the first experiment that proves it.” After all, familiar optical illusions permit different observers to “experience different, conflicting realities” in the sense of conflicting apparent realities. Of course, in such a case at least one of the “perceived realities” is indeed illusory, since they cannot both be veridical and also conflicting on pain of violating the Law of Non-Contradiction. But further perusal of the article dashes any hope of anything comprehensible in this way. The experiments in question are done on a system composed of only six photons. Obviously the photons do not experience anything at all, much less conflicting realities. What in the world is going on? In short, the way that this experiment is described—in terms of its significance—is complete nonsense. Physicists have become accustomed to spouting nonsense when quantum mechanics is the subject of discussion, which often takes the form of mind-blowing assertions about the loss of “classical reality” or even “classical logic”. The reason we know that all of this is nonsense right off the bat is that the experimental predictions of standard quantum mechanics can be accounted for—in several different ways—by theories that postulate an objective, unique physical reality governed by definite laws and using only classical logic and mathematics. So when the sorts of claims made in the title and abstract of the article are made, one knows immediately that they are unjustified hype. … Suppose, in other words, one were dead-set on maintaining that the physical world is local in the face of all the experimental evidence that it isn’t. How might that be done? It seems rather desperate but I suppose one might go so far as denying the very existence of any objective physical reality at all. Or, as I sometimes put it, “Nothing really exists, but thank God it is local”. But as should be obvious, this accomplishes nothing. If there is no objective physical world then there is no subject matter for physics, and no resources to account for the outcomes of experiments. There are many good books that correctly and clearly exposit the situation, including David Albert’s Quantum Mechanics and Experience, Travis Norson’s Foundations of Quantum Mechanics, Peter Lewis’s Quantum Ontology, Jean Bricmont’s Understanding Quantum Mechanics and Quantum Sense and Nonsense, and (co-incidentally) my own Philosophy of Physics Quantum Theory which happens to go on sale on March 19. Objective reality is safe and sound. We can all sleep well." -If There Is No Objective Physical World Then There Is No Subject Matter For Physics by Tim Maudlin
" Headline news! Stop the presses! A group of experimenters did an experiment, and the results came out exactly the way that our best physical theory of such things says it should, just as everyone expected. Quantum Theory Confirmed Again. That’s what actually happened, though you’d never know it from the clickbait headline: A quantum experiment suggests there’s no such thing as objective reality . The experiment  was inspired by a recent paper by Časlav Brukner, entitled “A No-Go Theorem for Observer-Independent Facts” . The abstract of the paper reporting on the experiment proclaims, “This result lends considerable strength to interpretations of quantum theory already set in an observer-dependent framework and demands for revision of those which are not.” Here’s a nice fact about claims of this sort: when you see one, you can be sure, without even going through the details of the argument, that any conclusion to the effect that the predictions of quantum mechanics are incompatible with an objective, observer-independent reality, is simply and plainly false. That is because we have a theory that yields all of the predictions of standard quantum mechanics and coherently describes a single, observer-independent world. This is the theory that was presented already in 1927 by Louis de Broglie, and was rediscovered in 1952 by David Bohm, and is either called the de Broglie-Bohm pilot wave theory, or Bohmian mechanics, depending on who you’re talking to. You can be confident that, if you went through the details of any real or imagined experiment, then you would find that the de Broglie-Bohm theory gives a consistent, observer-independent, one-world account of what happens in the experiment, an account that is in complete accord with standard quantum mechanics with regards to predictions of experimental outcomes." -Quantum Theory Confirmed Again by Wayne Myrvold
What about math, though? Doesn’t math show that our mind/sense apparatus is completely flawed, or some other such thing? Well, if that were true, then, again, we’d have to declare that we can’t validate the math, since it is being validated by flawed mind and senses. Some might argue that math is some kind of truth that can be validated beyond mind and senses, but, couldn’t a person have a dream where math followed really bizarre laws, and stood up to rigorous examination, and verification, and only realize that the math was nonsense upon awakening? The only way to realize that there is such a thing as real math, versus the fake math in the dream is concurrence with an existent, objective reality, and senses able to be in contact with it. These must exist, consistently in opposition to the dream version in order for this to make any sense in the first place. If everything were dream like, or at least our senses and mind were so screwed up that things may as well be as such, then we’d have nothing to hold math up to in the first place. Even if the laws of math seemed to make sense, without a real world it would be impossible to verify them.