Clear, Obscure, Distinct, and Confused Ideas and How They Relate to Definitions

I wanted to capture the meaning of these terms because they are very important in dealing with definitions.  The terms have a formal place in logic, and are often encountered in the traditional literature.  Yet it is also fair to say that we probably all use these terms (or their synonyms) quite frequently in analytical work.  Having a good idea of what they actually mean makes them, I think, more useful tools for us.

To get understandable definitions, I have used two sources: [1] C.S. Peirce's essay "How to Make Our Ideas Clear" (1879); and [2] Leibnitz's tract "Reflections Touching Knowledge, Truth, and Ideas" (1684).  This is because each source, in my opinion, is understandable for only two of the terms.  

Here we go.

• Clear: A clear idea is one which is so apprehended that it will be recognized wherever it is met with, and so that no other will be mistaken for it. [1]
• Obscure: A notion is obscure when it is not sufficient to enable us to recognize the thing which it represents: - when, for example, I remember some flower of animal which I have formerly seen but this remembrance is not sufficient to enable me to recognize its image or to discriminate it from others which resemble it. [2]

So ideas can be clear or obscure.  If an idea is obscure, we can go no further.  However, if an idea is clear, then it can be either distinct or confused. 

• Distinct: A distinct idea is one that contains nothing that is not clear.  This is technical language; by the contents [from the word "contains"] of an idea logicians understand whatever is contained in its definition.  So that an idea is distinctly apprehended according to them when we can give a precise definition of it in abstract terms. [1]
• Confused:  It [an idea] is confused when we are not able to enumerate marks sufficient to discriminate the thing from others [i.e. form a definition of it], although it may in reality have such marks and requisites into which its notion may be resolved...Thus [for example] we cannot explain to the blind what red is [even though it is clear idea]...In like manner we see that painters and other artists discern well enough what is well or ill done; but often are not able to give a reason for their judgement, and reply to those that inquire what it is that displeases them in the work, that there is something, they know not what, wanting. [2] 

Leibnitz took up the what Descartes had earlier said about clear and distinct ideas, but which Descartes and his followers had never been able to clarify.

I suppose we can summarize by saying an idea is clear when we can recognize it the next time we encounter it, and distinct when we have a good enough definition of it such that we can distinguish it from all other concepts. 

We can see that "clear" and "obscure" apply to ideas, but "distinct" and "confused" really only apply to definitions.