I was preparing a critical thinking lecture that included some C.S. Peirce and thought that I would present a variant of it to a wider audience. Since many of the SR and OOO crowd is more familiar with Whitehead than his predecessor Peirce, I hope that this is helpful and informative. Note that I have simplified it as befits an undergraduate course, and thus I have significantly rephrased some of the questions. That said, the re-phrasing might be more obviously informative.
"Questions Concerning Certain Faculties Claimed for Man"
Peirce asks seven questions in this article concerning thought and its ability to know.
Without previous knowledge or reasoning, can we immediately distinguish between introspection and perception?
We feel that we have this power or faculty, but there is no evidence that we do.
There is lots of evidence that we do not.
"Every lawyer knows how difficult it is for witnesses to distinguish between what they have seen and what they have inferred" (CP 5.216).
Two of the four sources of knowledge, introspection and perception, are not distinct.
Do we have an intuitive knowledge of ourselves, i.e., have self-consciousness?
"I" or self-reference has to be taught to children.
So does ascribing what others says to ourselves.
Do we have a power to distinguish subjective from objective elements of thought?
We have no intuitive power, but we have methods of verification.
Much of this follows from question 1.
Do we have a power of introspection, or is our knowledge of the internal world derived from observation of external facts?
Per question 3, we cannot know immediately.
The only way to investigate it is through psychology, but that is not based on introspection.
We cannot use non-introspective methods to prove the power of introspection.
Can thought reference nothing?
Thought is always about something.
Thought is intentional, although for Peirce we should understand this as originating from the thing, not mind.
Is anything unthinkable?
To be is synonymous with to be thinkable.
To be is to be related, which is to be thinkable.
Can we think things other than thought itself?
*The last few questions concern his semiotic. As for question 7, I suspect that it has significance for the OOO crowd and others worried about anthropocentrism.