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 might 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?
Note also that if you take Clifford's thesis to heart you will have to suspend belief on all sorts of questions outside of religion, questions in ethics, politics, economics, climatology, etc., questions you have extremely firm opinions about. The practical upshot, if one were consistent, would probably be a full retreat into Skeptic ataraxia. At least until the political authorities came to put you in prison. Then you would begin believing that some things are just and some are not, etc., and damn the insufficiency or nonexistence of the evidence for the contentious beliefs.
Our doxastic predicament is a bitch, ain't she? Well, what do you want for a Cave?
In Does Matter Think? I wrote:
I now add that I am using 'thinking' in the broad Cartesian sense that covers all intentional or object-directed experiences; but I also hold that non-intentional experiences are unintelligible to us on the basis of current physics. My thesis is that, given what we know about the physical world from current physics, it it unintelligible that the phenomena of mind, whether intentional or non-intentional, be wholly material in nature.
I grant that what is unintelligible to us might nevertheless be the case. But if such-and-such is unintelligible to us, then that is a fairly good reason to believe that it is not possibly the case. A theological example may help clarify the dialectical situation. Christians believe that God became man. Some will say that this is impossible in the strongest possible sense: logically impossible, i.e., in contravention of the Law of Non-Contradiction. For what the doctrine implies is that one person has both human and divine attributes, that one person is both passible and impassible, omniscient and non-omnisicent, etc. One response, a mysterian response, is to say that the doctrine of the Incarnation is true, and that therefore it is logically possible. The fact, if it is fact, that the Incarnation is unintelligible to us — where 'unintelligible' means: not understandable as possibly true in a broadly logical sense – does not show that the doctrine is impossible, but that it is a mystery: a true proposition that we, due to our limitations, cannot understand.
A materialist can make the same sort of move in one of two ways. He could say that our understanding of matter at present does not allow us to understand how conscious experience could be wholly material in nature, or he can say that our understanding of matter will never allow us to understand how conscious experience could be wholly material in nature. Either way, conscious experience, whether intentional or non-intentional, is wholly material in nature, and falls entirely within the subject-matter of physics, whether a future physics achievable by us, or a physics which, though not achievable by us, is perhaps achievable by organisms of a different constitution who study us.
If I understand Galen Strawson's view, it is the first. Conscious experience is fully real but wholly material in nature despite the fact that on current physics we cannot account for its reality: we cannot understand how it is possible. Here is a characteristic passage from Strawson:
Strawson and I agree on two important points. One is that what he calls experiential phenomena are as real as anything and cannot be eliminated or reduced to anything non-experiential. The other is that there is no accounting for experiential items in terms of current physics.
In the Comments Vlastimil V. asked:
It is matter as understood by current physics. And yes, one can know a priori that matter so conceived cannot think or feel. Note that I am not saying that matter anyhow conceived can be known a priori to be such that it cannot think or feel. I admit the very vague, very abstract, epistemic (and perhaps only epistemic) possibility that God or some super-intelligent extraterrestrial or even human being far in the future could get to the point of understanding how an experiential item like a twinge of pain could be purely material or purely physical. But this is really nothing more than an empty gesturing towards a 'possibility' that cannot be described except in the vaguest terms. It is nothing but faith, hope, and hand-waving.
An experiential item such as a twinge of pain or a rush of elation is essentially subjective; it is something whose appearing just is its reality. For qualia, esse = percipi. If I am told that someday items like this will be exhaustively understood from a third-person point of view as objects of physics, I have no idea what this means. The notion strikes me as absurd. We are being told in effect that what is essentially subjective will one day be exhaustively understood as both essentially subjective and wholly objective. If you tell me that understanding in physics need not be objectifying understanding, I don't know what that means either.
As Strawson clearly appreciates, one cannot reduce a twinge of pain to a pattern of neuron firings, for such a reduction eliminates the what-it-is-like-ness of the experience. And so he inflates the concept of the physical to cover both the physical and the irreducibly mental. But by doing this he drains the physical of definite meaning. His materialism is a vacuous materialism.
Strawson frankly confesses, "I am by faith a materialist." (p. 69) Given this faith, experiential items, precisely as experiential, must be wholly material in nature. This faith engenders the hope that future science will unlock the secret. Strawson must pin his hope on future science because of his clear recognition that experiential items are incomprehensible in terms of current physics.
But what do faith and hope have to do with sober inquiry? It doesn't strike me as particularly intellectually honest to insist that materialism just has to be true and to uphold it by widening the concept of the physical to embrace what is irreducibly mental. It would be more honest just to admit that the mind-body problem is insoluble.