The first is, that some are clear and others obscure; some distinct and others confused.

2.  Clear and obscure explained by Sight.

The perception of the mind being most aptly explained by words relating to the sight, we shall best understand what is meant by clear and obscure in our ideas, by reflecting on what we call clear and obscure in the objects of sight.  Light being that which discovers to us visible objects, we give the name of obscure to that which is not placed in a light sufficient to discover minutely to us the figure and colours which are observable in it, and which, in a better light, would be discernible.  In like manner, our simple ideas are clear, when they are such as the objects themselves from whence they were taken did or might, in a well-ordered sensation or perception, present them.  Whilst the memory retains them thus, and can produce them to the mind whenever it has occasion to consider them, they are clear ideas.  So far as they either want anything of the original exactness, or have lost any of their first freshness, and are, as it were, faded or tarnished by time, so far are they obscure.  Complex ideas, as they are made up of simple ones, so they are clear, when the ideas that go to their composition are clear, and the number and order of those simple ideas that are the ingredients of any complex one is determinate and certain.

3.  Causes of Obscurity.

The causes of obscurity, in simple ideas, seem to be either dull organs; or very slight and transient impressions made by the objects; or else a weakness in the memory, not able to retain them as received.  For to return again to visible objects, to help us to apprehend this matter.  If the organs, or faculties of perception, like wax over-hardened with cold, will not receive the impression of the seal, from the usual impulse wont to imprint it; or, like wax of a temper too soft, will not hold it well, when well imprinted; or else supposing the wax of a temper fit, but the seal not applied with a sufficient force to make a clear impression:  in any of these cases, the print left by the seal will be obscure.  This, I suppose, needs no application to make it plainer.

4.  Distinct and confused, what.

As a clear idea is that whereof the mind has such a full and evident perception, as it does receive from an outward object operating duly on a well-disposed organ, so a distinct idea is that wherein the mind perceives a difference from all other; and a confused idea is such an one as is not sufficiently distinguishable from another, from which it ought to be different.

5.  Objection.

If no idea be confused, but such as is not sufficiently distinguishable from another from which it should be different, it will be hard, may any one say, to find anywhere a confused idea.  For, let any idea be as it will, it can be no other but such as the mind perceives it to be; and that very perception sufficiently distinguishes it from all other ideas, which cannot be other, i.e. different, without being perceived to be so.  No idea, therefore, can be undistinguishable from another from which it ought to be different, unless you would have it different from itself:  for from all other it is evidently different.