Now some more about concepts:
Comprehensive_Manual_of_Abhidhamma trans. Bodhi
VIII. COMPENDIUM OF CONDITIONALITY p.325
Analysis of Concepts
There are such terms as “land,” “mountain,” and the like,
so designated on account of the mode of transition of the respective
elements; such terms as “house,” “chariot,” “cart,” and the like, so
named on account of the mode of formation of materials; such terms
as “person,” “individual,” and the like, so named on account of the
five aggregates; such terms as “direction,” “time,” and the like,
named according to the revolution of the moon and so forth; such
terms as “well,” “cave,” and the like, so named on account of the
mode of non-impact and so forth; such terms as kasióa signs and
the like, so named on account of respective elements and
distinguished mental development.
All such different things, though they do not exist in the ultimate
sense, become objects of consciousness in the form of shadows of
They are called concepts because they are thought of, reckoned,
understood, expressed, and made known on account of, in
consideration of, with respect to, this or that mode. This kind of
concept is so called because it is made known
Concepts can be classified in many ways. Things like a unicorn and God and rabbits horns can be considered as different types of pannati from trees. Trees, computers, humans, Robert, Kilaya, are the shadows of what is really there - and what is really there are only namas and rupas, mentality and matter, insignificant dhammas that can barely be said to exist because they pass away instantly. These concepts are more deluding than concepts like unicorns (which we know have no reality).
Because of accumulated avijja, ignorance, these type of concepts (pannatti) delude and instead of being given their correct status - as neccessary designations* - they are assumed to be actual. And that is where all problems begin and end.
*Note that these designations happen long before they are linguistic labels. What is called a thought in conventional language is comprised of billions of momentary arisings which repeatedly take a concept as object and may include mentally naming it. Becuase of this repetition - and the lack of insight into the actual dhammas - the illusion of permanence is solidified.
The commentary to the UDANA ( translation by Peter Masefield from PTS) (p71,vol1, enlightenment chapter)
it is ignorance since it causes beings to dart among becomings and so on within samsara…, it is ignorance since it darts among those things which do not actually exist [i.e. men, women etc] and since it does not dart among those things that do exist [.e. it cannot understand the khandas, paramattha dhammas].