No one here is saying that if you have an idea, that idea must have a perceptual object. To cite Hume's famous example, I have an idea of a golden mountain. Must I, therefore, have perceived a golden mountain? No, of course not. Ditto for perfect circles, etc. Does that mean that golden mountains and perfect circles are innate ideas. No. It simply means that we can abstract from our perceptions. But to get the idea of a golden mountain, you do need sensory input. E.g., you need perceptual evidence of gold color, etc. To get the idea of a perfect circle, you need perceptual evidence of lines and shapes, and so on. All we're saying is that perceptual evidence is required for concept formation.Neither of us (us: Brady and I) disputes the fact that experience is integral to concept formation in humans. What we contest is the idea that experiential content is sufficient for concept formation.
As for justifying our perceptions, a "perception," according to Objectivism, is the basis of awareness. But perception is not the sole basis of awareness. The presence of a perceiver having the cognitive faculties capable of perception is equally basic.
Therefore, a percept requires no justification, because it is not the sort of thing that can be mistaken.Would this perceptual infallibility also apply to perceptions formed by direct mental stimulus?
If not, your thesis is refuted.
If so, then your thesis becomes trivial-- since, by definition, a percept is just something perceived, a 'mistaken perception' is a contradiction in terms.
Now, you ask, but how do you know that every perceptual identification you make is not in error, since when you make an error, you're not aware of it? Well, the concept of an "error" is arrived at only by correctly identifying reality, in contrast to which I can then recognize an error, which is a departure from a correct identification. If I wasn't able to correctly identify reality, I wouldn't be able to correctly identify the fact that I had made an error. Nor would I have acquired the concept of "error" from the experience of having made one. The recognition of error presupposes the ability to identify reality correctly.There are such things as second-order errors. In logic, for example, mistakes made in a demonstration built upon false premises are second-order errors.
And the possibility of second-order errors is enough to refute your thesis that "If I wasn't able to correctly identify reality, I wouldn't be able to correctly identify the fact that I had made an error." For, in point of fact, you could identify errors within your perceptions if these perceptions or aspects of them contradicted either one another or the whole of your perceptual history. Moreover, in uncovering these errors, you could purge your perceptual history of all internal errors, and contemplate a coherent whole-- yet without any idea as to whether this whole corresponded properly to 'reality'.
Nor is it legitimate to posit the possibility of error without any evidence of it. From the fact that it's possible for people to be in error in some situations, it does not follow that it's possible for them to be in error in all situations.Neither does it follow that it's impossible for people to be in error in all situations.
If claims to knowledge require evidence and justification, then so do claims for the possibility of error. If there is no evidence for the possibility of error -- if all the relevant evidence supports and none contradicts -- then one is justified in claiming knowledge.In other words, one is justified in believing that one has knowledge. For a necessary condition of knowledge is truth, and justification in the sense you've given does not preclude the possibility that what one believes to be knowledge is in fact falsehood.