"In the fewest words possible, concepts are: _capacities to think about general characteristics._. The latter are sometimes positive, sometimes negative.
"There are degrees of complexity in the activity referred to above as 'thinking about general characteristics', and there are corresponding degrees of complexity in what is meant by processing concepts. To start with the simplest case: To process the concept of _red_ or the concept _dog_ is to possess the capacity to think about the characteristics _red_ or _dog_, in the sense of being able to recognize things as red things or as dogs when these are perceived; more generally, it is the capacity to recognize characteristics in perceived or otherwise intuited particulars. It is important to add that we can exercise this capacity whether or not we use or even possess such generals words as _red_ and _dog_, or such a proper name as _Cerberus_."
"This sort of case is the bare recognition of characteristics in particulars when the latter are before us and we perceive or intuit them. But there are more complicated kinds of thinking about characteristics that we can engage in while we are perceiving. To illustrate the point: if we perceive three apples, two of which are bright red and one a pale red, we can do all or some of the following things. We can recognize that all three apples possess the characteristic _red_; we can apprehend or judge that the characteristic _red_ is instantiated within our perceptual field; we can judge that the characteristic instantiated in two apples is different from and brighter than that instantiated in the third; we can judge that the characteristic _red_ is instantiated together with the characteristic of being an _apple_. All of these mental activities we can accomplish without the use of words or mental images, and persons possessing neither language nor an ability to form men
tal images could engage in them.
(White, F. C., 'On Schopenhauer's Fourfold Root of the Principle of Sufficient Reason',(Philosophy of History and Culture, Vol 8), pp.75-76)