I can only maintain, that is, affirm as necessarily valid for every one, that which produces conviction.Persuasion I may keep for myself, if it is agreeable to me; but I cannot, and ought not, to attempt to impose it as binding upon others.
Holding for true, or the subjective validity of a judgement in relation to conviction (which is, at the same time, objectively valid), has the three following degrees: opinion, belief, and knowledge.Opinion is a consciously insufficient judgement, subjectively as well as objectively.Belief is subjectively sufficient, but is recognized as being objectively insufficient.
Knowledge is both subjectively and objectively sufficient.
Subjective sufficiency is termed conviction (for myself); objective sufficiency is termed certainty (for all).I need not dwell longer on the explanation of such simple conceptions.
I must never venture to be of opinion, without knowing something, at least, by which my judgement, in itself merely problematical, is brought into connection with the truth- which connection, although not perfect, is still something more than an arbitrary fiction.
Moreover, the law of such a connection must be certain.For if, in relation to this law, I have nothing more than opinion, my judgement is but a play of the imagination, without the least relation to truth.
In the judgements of pure reason, opinion has no place.For, as they do not rest on empirical grounds and as the sphere of pure reason is that of necessary truth and a priori cognition, the principle of connection in it requires universality and necessity, and consequently perfect certainty- otherwise we should have no guide to the truth at all.Hence it is absurd to have an opinion in pure mathematics; we must know, or abstain from forming a judgement altogether.The case is the same with the maxims of morality.For we must not hazard an action on the mere opinion that it is allowed, but we must know it to be so.
In the transcendental sphere of reason, on the other hand, the term opinion is too weak, while the word knowledge is too strong.From the merely speculative point of view, therefore, we cannot form a judgement at all.For the subjective grounds of a judgement, such as produce belief, cannot be admitted in speculative inquiries, inasmuch as they cannot stand without empirical support and are incapable of being communicated to others in equal measure.
But it is only from the practical point of view that a theoretically insufficient judgement can be termed belief.Now the practical reference is either to skill or to morality; to the former, when the end proposed is arbitrary and accidental, to the latter, when it is absolutely necessary.
If we propose to ourselves any end whatever, the conditions of its attainment are hypothetically necessary.The necessity is subjectively, but still only comparatively, sufficient, if I am acquainted with no other conditions under which the end can be attained.On the other hand, it is sufficient, absolutely and for every one, if I know for certain that no one can be acquainted with any other conditions under which the attainment of the proposed end would be possible.In the former case my supposition- my judgement with regard to certain conditions- is a merely accidental belief; in the latter it is a necessary belief.The physician must pursue some course in the case of a patient who is in danger, but is ignorant of the nature of the disease.He observes the symptoms, and concludes, according to the best of his judgement, that it is a case of phthisis.
His belief is, even in his own judgement, only contingent: another man might, perhaps come nearer the truth.Such a belief, contingent indeed, but still forming the ground of the actual use of means for the attainment of certain ends, I term Pragmatical belief.
The usual test, whether that which any one maintains is merely his persuasion, or his subjective conviction at least, that is, his firm belief, is a bet.It frequently happens that a man delivers his opinions with so much boldness and assurance, that he appears to be under no apprehension as to the possibility of his being in error.The offer of a bet startles him, and makes him pause.Sometimes it turns out that his persuasion may be valued at a ducat, but not at ten.
For he does not hesitate, perhaps, to venture a ducat, but if it is proposed to stake ten, he immediately becomes aware of the possibility of his being mistaken- a possibility which has hitherto escaped his observation.If we imagine to ourselves that we have to stake the happiness of our whole life on the truth of any proposition, our judgement drops its air of triumph, we take the alarm, and discover the actual strength of our belief.Thus pragmatical belief has degrees, varying in proportion to the interests at stake.
Now, in cases where we cannot enter upon any course of action in reference to some object, and where, accordingly, our judgement is purely theoretical, we can still represent to ourselves, in thought, the possibility of a course of action, for which we suppose that we have sufficient grounds, if any means existed of ascertaining the truth of the matter.Thus we find in purely theoretical judgements an analogon of practical judgements, to which the word belief may properly be applied, and which we may term doctrinal belief.Ishould not hesitate to stake my all on the truth of the proposition-if there were any possibility of bringing it to the test of experience- that, at least, some one of the planets, which we see, is inhabited.Hence I say that I have not merely the opinion, but the strong belief, on the correctness of which I would stake even many of the advantages of life, that there are inhabitants in other worlds.