As Brooks says: "A concept cannot be represented by a concrete image. This is evident from its being general rather than particular. If its color, size or shape is fixed by an image, it is no longer general but particular." And Halleck says: "It is impossible to image anything without giving that image individual marks. The best mental images are so definite that a picture could be painted from them. A being might come under the class _man_ and have a snub nose, blonde hair, scanty eyebrows, and no scar on his face. The presence of one of these individual peculiarities in the concept _man_ would destroy it. If we form an image of an apple, it must be either of a yellow, red, green, or russet apple, either as large as a pippin or as small as a crab-apple. A boy was asked what he thought of when '_apple_' was mentioned. He replied that he thought of 'a big, dark-red, apple with a bad spot on one side, near the top.' That boy could image distinctly, but his power of forming concepts was still in its infancy." So we see that while a mental image must picture the particular and individual qualities, properties and appearances of some particular unit of a class, a _concept_ can and must contain only the _class qualities_--that is, the qualities belonging to the entire class. The general concept is as has been said "a general idea ... a general notion which has in it all that is common to its own class." And it follows that a "general idea" of this kind cannot be pictured. A picture must be of some particular thing, while a concept is something above and higher than particular things. We may picture _a man_, but we cannot picture Man the concept of the race. A concept is not a reproduction of the image of a _thing_, but on the contrary is _an idea of a class of things_. We trust that the student will consider this point until he arrives at a clear understanding of the distinction, and the reason thereof.