Maverick Philosopher: Strictly Philosophical

Is It Sometimes Rational to Believe on Insufficient Evidence?

I should think so.

The notion that we should always and everywhere apportion belief to evidence in such a way that we affirm only that for which we have sufficient evidence ignores the fact that belief for beings like us subserves action. If one acted only on those beliefs for which one had sufficient evidence one  would not act as one must to live well.

 

When a young person believes that he or she can do such-and-such, it is almost always on the basis of insufficient evidence.  And yet such belief beyond the evidence is a sine qua non of success.  There are two necessary conditions of success in life: one must believe that what one proposes to do is worth doing, and one must believe that one is capable of doing it.  In both cases one believes and acts on evidence that could hardly be called sufficient. 

As a young man observing my professors, I said to myself, "I can do this and I can do it better!"  (It can be advantageous to have mediocre teachers!) My belief in myself was not without evidence but surely was not grounded in sufficient evidence. (Suppose we agree that sufficient evidence for proposition p renders p more likely than not.)  My believing in myself was a believing well beyond the evidence. But my belief in self, even unto cockiness, was sine qua non for my success.  Effort follows belief.  In cases like these, belief is a matter of the will: one chooses to believe that a certain good is attainable despite the insufficiency of the evidence the intellect can gather at the time.

This strikes me as a good maxim:  Don't let insufficient evidence prevent you from believing what you are better off believing than not believing. 

Let's consider another example.

The New Neighbors

What evidence do I have that my new neighbors are morally decent people? Since they have just moved in, my evidence base is exiguous indeed and far from sufficient to establish that they are decent people. (Assume that some precisifying definition of 'decent' is on the table.) Should I suspend judgment and behave in a cold, skeptical, stand-offish way toward them? ("Prove that you are not a scumbag, and then I'll talk to you.") Should I demand of them 'credentials' and letters of recommendation before having anything to do with them? Either of these approaches would be irrational.

A rational being wants good relations with those with whom he must live in close proximity and whose help he may need. Wanting good relations, he must choose means that are conducive to that end. Knowing something about human nature, he knows that 'giving the benefit of the doubt' is the wise course when it comes to establishing relations with other people. If you begin by impugning the integrity of the other guy, he won't like you.  One must assume the best about others at the outset and adjust downwards only later and on the basis of evidence to the contrary. But note that my initial belief that my neighbors are decent people -- a belief that I must have if I am to act neighborly toward them -- is not warranted by anything that could be called sufficient evidence. Holding that belief, I believe way beyond the evidence. And yet that is the rational course.

So again we see that in some cases, to refuse to believe beyond the evidence is positively irrational. A theory of rationality adequate for the kind of beings we are cannot require that belief be always and everywhere apportioned to evidence.

Evidence and Actuality: A Modal Punch at W. K. Clifford

W. K. Clifford is often quoted for his asseveration that "it is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence."  Now one of my firmest beliefs is that I am an actual individual, not a merely possible individual. A second is my belief that while there is an infinity of possible worlds, there is exactly one actual world and that this world of me and my world mates is the world that happens to be actual.  (Think of the actual world as the total way things are, and of a merely possible world as a total way things could have been.  For a quick and dirty primer, see Some Theses on Possible Worlds.)

But not only do I have insufficient evidence for these two beliefs, it looks as if I have no evidence at all.  And yet I feel wholly entitled to my acceptance of them and in breach of no plausible ethics of belief, assuming there is such a subject as the ethics of belief.

Consider the following argument that I adapt from D. M. Armstrong, who borrowed it from Donald C. Williams:

1. Exactly one of the infinity of possible worlds is actual.

2. This world of me and my mates is a possible world.

Therefore, very probably,

3. This world of me and my mates is merely possible.

This is an inductive argument, but a very strong one.  While it does not necessitate its conclusion, it renders the conclusion exceedingly likely.  For if there is an infinity of worlds, how likely is it that mine is the lucky one?

And yet the conclusion is absurd, or to be precise: manifestly false.  Is it not perfectly obvious that this world of ours and everything in it is actual?  I am convinced that I am actual, and that all this stuff I am interacting with is actual.  I am sitting in an actual chair in an actual room which is lit by an actual sun, etc. 

But how do I know this?  What is my evidence?  There are no facts known to me that are better known than the fact that I am actual (that I actually exist).  So my evidence cannot consist of other facts.  Is it self-evident that I am actual?  You could say this, but how do I know, given the above argument, that my actuality is objectively self-evident as opposed to merely subjectively self-evident?  Subjective self-evidence is epistemically worthless, while objective self-evidence is not to be had in the teeth of the above argument.  No doubt I seem to myself to be actual.  But that subjective seeming does not get the length of objective self-evidence.  I now argue as follows:

4. If it is wrong to believe anything on insufficient evidence, then it is wrong to believe anything on no evidence.

5. I have no evidence that me and my world are actual.

6. It is not wrong to believe what is obviously true.

7. It is obviously true that I am actual.

Therefore, contra Clifford,

8.  There are some things it is not wrong to believe on insufficient evidence.

This is not a compelling argument, but it is a very powerful one.  Not compelling because the Cliffordian extremist could bite the bullet by denying (7).  He might say that the ethics of belief enjoins us to suspend belief on the question whether one is actual.  

Now this is psychologically impossible, for me anyway.  But apart from this impossibility, it is surely better known that I am actual than that Clifford's extreme thesis is true.

There are other obvious problems with the thesis.  Any tyro in philosophy should see right away that it is self-vitiating.  If it is wrong to believe anything on insufficient evidence, then it is wrong to believe Clifford's thesis on insufficient evidence.  But what conceivable evidence could one have for it?  None that I can see.  It is not only a normative claim, but one stuffed with universal quantifiers.  Good luck!  If you say that the thesis needn't be taken as applying to itself, then other problems will arise that you can work out for yourself.  Why do I have to do all the thinking?