23. THE THEORY OF DISTINCTIONS IN ITS APPLICATION TO THE QUESTION.—In the next place, what are we to understand by a _real_ distinction in this matter? Ambiguity and obscurity of thought in regard to the theory of _distinctions_, and in regard to the application of the theory to the present question, has been probably the most fertile source of much tedious and fruitless controversy in this connexion. Anticipating what will be considered more fully at a later stage (30), we must note here the two main classes of distinction which, by reflecting on our thought-processes, we discover between the objects of our thought. The _real_ distinction is that which exists in things independently of the consideration of our minds; that which is discovered, but not made, by the mind; that which is given to us in and with the data of our experience. For example, the act of thinking is a reality other than, and therefore _really_ distinct from, the mind that thinks; for the mind persists after the act of thinking has passed away. Opposed to this is the mental or logical distinction, which is the distinction made by the mind itself between two different concepts of one and the same reality; which is not in the reality independently of our thought, but is introduced into it by our thought, regarding the same reality under different aspects or from different points of view. The mind never makes such a distinction without some ground or reason for doing so. Sometimes, however, this reason will be found exclusively in the mind itself—in the limitations of its modes of thought—and not in the reality which is the matter or object of the thought. The distinction is then said to be _purely_ logical or mental. Such distinctions are _entia rationis_, logical entities. An example would be the distinction between the concept “man” and the concept “rational animal,” or, in general, between any definable object of thought and its definition; the distinction, therefore, between the essence and the existence of the Necessary Being is a purely logical distinction, for in a definition it is the essence of the thing we define, and existence is of the essence or definition of the Necessary Being.