Epistemological questions: “What can I know? How can I distinguish those things I am justified in believing from those things I am not justified in believing? And how can I decide whether I am more justified in believing one thing than in believing another?”

Philosophical skeptics: There are philosophers who doubt whether there is anything that we can know. They also doubt, therefore, whether it is possible for us to find out whether there is anything that we can know.

Epistemologists’ faith in themselves: In making their assumptions, epistemologists presuppose that they are rational beings. This means, in part, that they have certain properties which are such that, if they ask themselves, with respect to anyone of these properties, whether or not they have that property, then it will be evident to them that they have it. It means further that they are able to know what they think and believe and that they can recognize inconsistencies. Epistemologists presuppose, then, that they can succeed. This means, therefore, that they have a kind of faith in themselves.

Include and Entail: One property may be said to include another if the first is necessary such that anything that has it also has the second. And the property of being F may be said to be entail the property of being G provided that believing something to be F includes believing something to be G.

Intentional and sensible properties: Some self-presenting properties pertain to our thoughts – thinking, judging, hoping, fearing, wishing, wondering, desiring, loving, hating, and intending. And some of them have to do with the ways in which we sense, or are appeared to. The first may be called intentional properties and the second may be called sensible properties. Both types must be taken into consideration in any adequate theory of knowledge.

In saying, “I know,” I give my hearers a kind of guarantee and stake my reputation, but in saying “It seems to me,” I play it safe, indicating that what I say carries no guarantee at all, and that anyone choosing to believe what I say does so at his or her own risk. Besides, we must distinguish the belief that a speaker has about the words he is using from the belief that he is using those words to express. What holds true for the former need not hold true for the latter.

Withholding: A person may be said to withhold a proposition h provided he does not believe h and does not believe the negation of h. The proposition that God exists is such that the theist accepts it, the atheist accepts its negation, and the agnostic withholds it.

The counterbalanced: If a proposition is counterbalanced for a given subject, then neither the proposition nor its negation has any positive degree of epistemic justification for that subject.

The probable and more probable: If a proposition is not counterbalanced for S, then either that proposition or its negation is probable for S.To say that a proposition is probable for us, in this fundamental sense, is to say simply that we are more justified in believing that proposition than in believing its negation.You are more justified in believing that you will be alive six months from now than in believing that you will be alive a year from now. In this case, we may say, of two propositions each of which is merely probable for you, that one of them is more probable for you than the other.

Beyond reasonable doubt: The category of being beyond reasonable doubt is illustrated by the proposition that the building in which I now find myself will be here tomorrow. The proposition is not evident. But for me – and I hope that for others – the proposition is such that believing it is more justified than withholding it.

The evident: The evident proposition, like one that is beyond reasonable doubt, is a proposition which is such that one has more justification for believing it than for withholding it. And the evident has this further feature: for any two propositions, if one of them is evident, then believing the one that is evident is at least as justified as withholding the other – whatever epistemic status the other may have.

The certain: this concept is illustrated by those propositions about mental life that are sometimes called “self-presenting.” It is also illustrated by certain logical and metaphysical axioms that from the basis of what we know a priori.

The 13 steps

We note, finally, that our undefined epistemic concept and the axioms that may be provided for it enable us to set forth a hierarchy of epistemic concepts. This hierarchy involves 13 epistemic categories – 13 steps or stages each capable of being occupied by countless propositions.

To see the point of such a hierarchy, let us turn back to the concept of the evident.  An evident proposition is one that is justified. But there are many justified propositions that are not evident. Indeed many propositions that may be said to have a very high degree of justification are not evident. For example, it may be evident to you now that you have walked today and that you also walked yesterday and the day before that. You may have very good grounds for accepting the proposition that you will walk tomorrow and the day after that: the proposition may be strongly supported by induction. But it is not now evident to you or to anyone else that you will walk tomorrow. For no one now knows that you will walk tomorrow.

The preposition that you will walk tomorrow may be beyond reasonable doubt for you. But nothing that you can find out today can make it evident for you today that you will walk tomorrow.

The difference between what is evident and what is beyond reasonable doubt but not evident is not a mere quantitative difference it is a qualitative difference, like that between being in motion and being at rest. It is also comparable to the distinction between the situations wherein one is conscious and has auditory sensations and that wherein one is conscious and has no auditory sensations. And it is comparable to the distinction between the situation wherein one is alive and conscious and that wherein one is alive but not conscious.

Propositions that are counterbalanced may be thought of as occupying the Zero-level. Those that are probable may be thought of as occupying the lowest positive epistemic level. Above these are propositions that are beyond reasonable doubt. Still higher are propositions that are evident. And at the top of the hierarchy are those propositions that are certain.

There are two additional positive steps or levels that we have not mentioned. One is the step between that which is probable and that which is beyond reasonable doubt. Propositions in this category may be “epistemically in the clear.” A proposition is said to be epistemically in the clear for a subject S provided only that S is not pre justified in withholding that proposition than in believing it. The other positive step falls between the evident and the certain; propositions in this category are said to be “obvious.” A proposition p is said to be obvious for a subject S provided only that, for every position q, S is more justified in believing p than in withholding q.

So far, we have one zero level and six positive levels. We may now go on to distinguish six negative levels. The negative level that a proposition occupies is a function of positive level of its negation. Thus the “highest” negative level that a proposition p may occupy for a subject S is that of being such that its negation is probable for S. And the “lowest” negative level is that of having a negation that is certain for S.

Our epistemic hierarchy, then, may be put this way:

6. Certain

5. Obvious

4. Evident

3. Beyond Reasonable Doubt

2. Epistemically in the Clear

1. Probable

0. Counterbalanced

-1.  Probably False

-2. In the Clear to Disbelieve

-3. Reasonable to Disbelieve

-4. Evidently False

-5. Obviously False

-6. Certainly False

The first five categories are such that each includes but is not included in the categories listed immediately below it. And the last five categories are such that each includes but is not included in the categories listed immediately above it. [A further principle that is needed to complete our hierarchy of 13 steps may be summarized this way: If a proposition p epistemically in the clear for S, then p is probable for S. Instances of it are: “If agnosticism is not more justified for S than theism, then theism is more justified for S than atheism”; and “If agnosticism is not more justified for S than atheism, then atheism is more justified for S than theism.” The point of including this principle here is to insure that whatever is epistemically in the clear is also probable.]

To see the point of such a hierarchy, let us turn back to the concept of the evident. An evident proposition is such that is justified. But there are many justified propositions that are not evident. Instead many propositions that may be said to have a very high degree of justification are not evident. For example, it may be evident to you now that you have walked today and that you also walked yesterday and the day before that. You may have very good grounds for accepting the proposition that you will walk tomorrow and the day after that: the proposition may be strongly supported by induction. But it is not now evident to you or to anyone else that you will walk tomorrow, for no one now knows that you will walk tomorrow.

The proposition that you will walk tomorrow may be beyond reasonable doubt for you, but nothing that you can find out today can make it evident for you today can make it evident for you today that you will walk tomorrow.

Source: Theory of Knowledge, by: Roderick M.Chisholm