The process of classifying objects and the use of language depend upon the power of judgment; for if we see an object possessing certain qualities, in order to apply the name we must compare and observe their resemblance to the qualities to which such a name has been applied in past experience, and this feeling of resemblance is an act of judgment. The application of a name, then, always implies the exercise of the power of judgment, by which a comparison is made between the present qualities observed in an object and the same qualities which affected the mind when the name has formerly been employed. It also implies the act of association, by which the perception of certain qualities recalls the idea of the sound or object with which they have been repeatedly conjoined.
The mental process called _reasoning_ is nothing but a connected succession of acts of judgment. It is a comparison of what is asserted in a given proposition with some truth which is believed, or which has been established by evidence, and then observing the agreement or disagreement. Thus the truth that "things will be in agreement with past experience unless there is some reason for the contrary," is a truth which every mind believes. Whenever, therefore, any event has been repeatedly an object of past experience, it is compared with this truth already believed, and found to be included under it, and therefore entitled to the same credit.
Thus, also, the truth that "things which equal the same thing equal one another," is one which every mind believes. When any object by examination is found to be included under that class of objects which are thus equal to the same thing, it is an act of reasoning when we infer that they are equal to one another.
Having examined the intellectual powers, we will now attend to the next general class, denominated _the susceptibilities_.
When the mind is in a state of emotion, this state is always either pleasurable or painful. _Desire_ relates to the attainment of some object which will be the cause of pleasurable emotions, or else to the avoidance of something which will cause painful emotions. This desire for pleasure and for the avoidance of pain is the mainspring of all mental activity; for when it is not in existence, neither the powers of the mind or of the body are called into exercise.