"[l]f there were no place for conventional phenomena, the existence of which is established by the epistemic instruments, these phenomena would be like the snake - that is,
the rope grasped as a snake - of which no cause or effect is possible. . . .
[l]f one were forced to maintain that there is no place for bondage, liberation, etc in the
meaning of “conventional existence/’ and that these must be placed only in the erroneous perspective, that would be a great philosophical error.
Even worse, as long as convention is conceived [as entirely nonexistent], since there
would be no role for the epistemic instruments, neither the proposition maintained nor
the person who maintains it nor the proof - including scriptural sources and reasoning - could be established by epistemic instruments. So it would be ridiculous to maintain
that there are no genuine phenomena delivered by the epistemic instruments.” {Ocean
30-31 )15Tsong khapa makes it plain here that conventional phenomena, unlike the snake
thought to be perceived when one sees a rope, have causes and effects, and are
actual. Moreover, he argues that the repudiation of the reality of the conventional
would undermine the possibility of epistemic authority, undermining even the abil-
ity to argue cogently that the conventional does not exist. Such a position would
be self-refuting.
-Jay Garfield, Taking Conventional Truth Seriously
One cannot refute too much of reality without self refuting. If almost nothing is real, or even so far as absolutely nothing is real, then, one’s position is also unreal, and untenable. Thus, reality is irrefutable. It may be critiqued, as Classical Theravada does, by pointing out what is real and what is merely an interpretation of the real, like paramattha vs pannatti, and so on, this is valid. But claims that ostensibly destroy all or most of reality turn the sword of destructive logic on themselves. They are built on a scaffolding of shared logic and convention, and just common sense, and the scaffolding collapses when they deny that the foundations of it exist, leaving them with no valid position, at all.
In other words, how many of us have spoken with someone who claims “Life is a dream, all is mind, nothing is real, nothing exists, Etc.” And then wondered how they justify sitting in an office, working all day to pay bills, and buy food, if they believe none of those things exist? The answer? They don’t, their philosophy is self refuting.