Conception is a state of mind similar to perception, and differs from it in being less vivid, and in not being produced through the medium of the senses.
When we look at a tree, we have a perception of this object. But the mind can also have an idea of this tree when removed from the sight, though the idea is not so vivid and distinct, nor have the senses any agency in producing it. The perfume of a rose, also, occasions another sensation; but when the rose is removed, so as not to affect the senses, we can still have a conception of its perfume. The conception differs from the perception only in being less vivid, and in not being caused by a material object acting on the senses.
Memory is either a conception or a perception, which is attended with a feeling of its resemblance to a past state of mind. It is this feeling of resemblance that is the only circumstance which distinguishes memory from conception.
Thus we may conceive of a tree without recognizing it as the particular idea of any tree we may have seen before; but if this is accompanied by a feeling of the resemblance of this idea to the one we always have when we see the tree that shadows the paternal roof, this conception becomes memory. If we conceive the form of a man without recognizing the resemblance of this idea to the perceptions we have when we see any particular man, this is a simple act of conception; but if we recognize in this object of conception the features of a dear friend, this act then becomes memory. Again, if we conceive of certain events and circumstances attending them without recognizing this combination as ever having existed in past experience, they are mere conceptions; but if we recognize in them the events and circumstances of past experience, conception becomes memory.
Imagination is the power which the mind possesses of arranging our conceptions in new combinations. We can conceive objects as united together of which we never conceived before as thus united.
Thus, when we read the description of some picturesque scene in nature, the mind immediately groups together mountains, trees, brooks, cottages, and glens, forming a new combination of conceptions different from any scene we ever witnessed or conceived before. All the objects thus combined are conceptions; the act of arranging them is an act of the imagination.
Judgment is the power which the mind possesses of noticing relations. A relation is an idea obtained by observing one thing in connection with another. Thus, when we perceive one thing to be longer than another, one thing to be on another, or one thing to belong to another—in all these cases the mind notices relations, or exercises the faculty of judgment. Thus, also, when we compare any action with the rule of duty in order to decide whether it is right or wrong, we exercise the same faculty. This act always is necessarily preceded by the comparison of one thing with another, in order to notice the relations.
Abstraction is the power of noticing certain parts or qualities of any object, as distinct from other parts or qualities. Thus, when we notice the length of a bridge without attending to the breadth or color, or when we notice the height of a man without thinking of his character, we exercise the faculty of abstraction.
Attention is the direction of the mind to any particular object or quality, from the interest which is felt in it, or in something connected with it. The degree of attention is always proportioned to the degree of interest felt in the object.
Association is the power possessed by the mind of recalling ideas in the connections and relations in which they have existed in past experience. For example, when any two objects, such as a house and a tree, have often been observed together, the idea of one will ordinarily be attended by that of the other. If two events have often been united together in regard to the time of their occurrence, such, for example, as thunder and lightning, the idea of one will usually be attended by the other.