Now, here arises a question on which the solution of the present difficulty will depend. Does it happen in all these relations that when one of the objects is presented to the senses or memory the mind is not only carried to the conception of the correlative, but reaches a steadier and stronger conception of it than otherwise it would have been able to attain? This seems to be the case with that belief which arises from the relation of cause and effect. And I shall add that it is conformable to the ordinary wisdom of nature to secure so necessary an act of the mind by some instinct or mechanical tendency, which may be infallible in its operations, may discover itself at the first appearance of life and thought, and may be independent of all the laboured deductions of the understanding. _II.--On Miracles_ A wise man proportions his belief to the evidence. In such conclusions as are founded on an infallible experience he expects the event with the last degree of assurance, and regards his past experience as a full _proof_ of the future existence of that event. In other cases he proceeds with more caution. He weighs the opposite experiments. He considers which side is supported by the greatest number of experiments; to that side he inclines with doubt and hesitation, and when at last he fixes his judgment, the evidence exceeds not what we properly call _probability_. All probability, then, supposes an opposition of experiments and observations, where the one side is found to overbalance the other, and to produce a degree of evidence proportioned to the superiority. When the fact attested is such a one as has seldom fallen under our observation, here is a contest of two possible experiences, of which the one destroys the other as far as its force goes, and the superior can only operate on the mind by the force which remains. The very same principle of experience which gives us a certain degree of assurance in the testimony of witnesses gives us also, in this case, another degree of assurance against the fact which they endeavour to establish, from which consideration there necessarily arises a counterpoise, and mutual destruction of belief and authority. But in order to increase the probability against the testimony of witnesses, let us suppose that the fact which they affirm, instead of being only marvellous, is really miraculous; and suppose also that the testimony, considered apart and in itself, amounts to an entire proof, of which the strongest must prevail, but still with a diminution of its force in proportion to that of its antagonist.