_Reader._ The term is known, but it is used more or less properly by different persons. Our minds may deal with either sensible or intellectual objects. When we have seen a mountain, we may think of it, because we have received from it an impression in our senses which leaves a vestige of itself in our organism, and enables us to represent to ourselves the object we have perceived. In this case our _thought_ is an exercise of our imagination. When, on the contrary, we think of some abstract notion or relation which does not strike our senses, and of which no image has been pictured in our organic potencies, then our _thought_ is an exercise of intellectual power. In both cases our brain has something to do with the thought. For in the first case our thought is an act of the sensitive faculty, which reaches its object as it is pictured, or otherwise impressed, in our organic potencies, of which the headquarters are in the brain. In the second case our thought is an act of the intellectual faculty, which detects the intelligible relations existing between the objects already perceived, or between notions deduced from previous perceptions; and this act, inasmuch as it implies the consideration of objects furnished to the mind by sensible apprehension, cannot but be accompanied by some act of the imaginative power making use of the images pictured in the organic potencies. Now, doctor, when you say that “the brain is the seat and organ of thought,” do you mean that both the intellectual and the imaginative thought reside in the brain and are worked out by the brain? _Büchner._ Of course. For “comparative anatomy shows that through all classes of animals, up to man, the intellectual energy is in proportion to the size and material quality of the brain” (p. 107).