Or, to take another illustration, the bird which saw three men go into a building, and inferred that one must still have remained when only two came out, conducted the inference receptually: the only data she had were those supplied by differential sense-perceptions. But although these data were sufficient for the purpose of conducting what Mr. Mivart calls a “practical inference,” and so of enabling her to know that a man still remained behind, they were clearly not enough to enable her to know the numerical relations _as_ relations, or in any way to predicate to herself, 3-2=1. In order to do this, the bird would have required to quit the region of receptual knowledge, and rise to that of conceptual: she would have required in some form or another to have substituted symbols for ideas. It makes no difference, so far as this distinction is concerned, when we learn that in dealing with certain savages “each sheep must be paid for separately: thus, suppose two sticks of tobacco to be the rate of exchange for one sheep, it would sorely puzzle a Dammara to take two sheep and give him four sticks.”[130] All that such facts show is that in some respects the higher receptual life of brutes attains almost as high a level of ideation as the lower conceptual life of man; and although this fact no doubt greatly lessens the difficulty which my opponents allege as attaching to the supposition that the two were genetically continuous, it does not in itself dispose of the psychological distinction between a recept and a concept. This distinction, as we have now so often seen, consists in a recept being an idea which is not itself an object of knowledge, whereas a concept, in virtue of having been named by a self-conscious agent, is an idea which stands before the mind of that agent _as_ an idea, or as a state of mind which admits of being introspectively contemplated as such. But although we have in this distinction what I agree with my opponents in regarding as the greatest single distinction that is to be met with in psychology, I altogether object to their mode of analyzing it. For what they do is to take the concept in its most highly developed form, and then contrast this with the recept of an animal. Nay, as we have seen, they even go beyond a concept, and allege that “the simplest element of thought” is a judgment as bodied forth in a proposition—_i.e._ _two_ concepts _plus_ the predication of a relationship between them! Truly, we might as well allege that the simplest element of matter is H_{2}SO_{4}, or the simplest element of sound a bar of the C Minor Symphony. Obviously, therefore, or as a mere matter of the most rudimentary psychological analysis, if we say that the simplest element of thought is a judgment, we must extend the meaning of this word from the mental act concerned in full predication, to the mental act concerned in the simplest conception.