separable are also distinguishable, and that whatever objects are distinguishable, are also different.  For how is it possible we can separate what is not distinguishable, or distinguish what is not different?  In order therefore to know, whether abstraction implies a separation, we need only consider it in this view, and examine, whether all the circumstances, which we abstract from in our general ideas, be such as are distinguishable and different from those, which we retain as essential parts of them.  But it is evident at first sight, that the precise length of a line is not different nor distinguishable from the line itself. nor the precise degree of any quality from the quality.  These ideas, therefore, admit no more of separation than they do of distinction and difference.  They are consequently conjoined with each other in the conception; and the general idea of a. line, notwithstanding all our abstractions and refinements, has in its appearance in the mind a precise degree of quantity and quality; however it may be made to represent others, which have different degrees of both.

Secondly, it is contest, that no object can appear to the senses; or in other words, that no impression can become present to the mind, without being determined in its degrees both of quantity and quality.  The confusion, in which impressions are sometimes involved, proceeds only from their faintness and unsteadiness, not from any capacity in the mind to receive any impression, which in its real existence has no particular degree nor proportion.  That is a contradiction in terms; and even implies the flattest of all contradictions, viz. that it is possible for the same thing both to be and not to be.

Now since all ideas are derived from impressions, and are nothing but copies and representations of them, whatever is true of the one must be acknowledged concerning the other.  Impressions and ideas differ only in their strength and vivacity.  The foregoing conclusion is not founded on any particular degree of vivacity.  It cannot therefore be affected by any variation in that particular.  An idea is a weaker impression; and as a strong impression must necessarily have a determinate quantity and quality, the case must be the same with its copy or representative.

Thirdly, it is a principle generally received in philosophy that everything in nature is individual, and that it is utterly absurd to suppose a triangle really existent, which has no precise proportion of sides and angles.  If this therefore be absurd in fact and reality, it must also be absurd in idea; since nothing of which we can form a clear and distinct idea is absurd and impossible.  But to form the idea of an object, and to form an idea simply, is the same thing; the reference of the idea to an object being an extraneous denomination, of which in itself it bears no mark or character.  Now as it is impossible to form an idea of an object, that is possest of quantity