To this I reply, that in judging of the actions of men we must proceed upon the same maxims, as when we reason concerning external objects. When any phenomena are constantly and invariably conjoined together, they acquire such a connexion in the imagination, that it passes from one to the other without any doubt or hesitation. But below this there are many inferior degrees of evidence and probability, nor does one single contrariety of experiment entirely destroy all our reasoning. The mind balances the contrary experiments, and, deducting the inferior from the superior, proceeds with that degree of assurance or evidence, which remains. Even when these contrary experiments are entirely equal, we remove not the notion of causes and necessity; but, supposing that the usual contrariety proceeds from the operation of contrary and concealed causes, we conclude, that the chance or indifference lies only in our judgment on account of our imperfect knowledge, not in the things themselves, which are in every case equally necessary, though, to appearance, not equally constant or certain. No union can be more constant and certain than that of some actions with some motives and characters; and if, in other cases, the union is uncertain, 'tis no more than what happens in the operations of body; nor can we conclude any thing from the one irregularity which will not follow equally from the other. 'Tis commonly allowed that madmen have no liberty. But, were we to judge by their actions, these have less regularity and constancy than the actions of wise men, and consequently are farther removed from necessity. Our way of thinking in this particular is, therefore, absolutely inconsistent; but is a natural consequence of these confused ideas and undefined terms, which we so commonly make use of in our reasonings, especially on the present subject. We must now show, that, as the _union_ betwixt motives and actions has the same constancy as that in any natural operations, so its influence on the understanding is also the same, in _determining_ us to infer the existence of one from that of another. If this shall appear, there is no known circumstance that enters into the connexion and production of the actions of matter that is not to be found in all the operations of the mind; and consequently we cannot, without a manifest absurdity, attribute necessity to the one, and refuse it to the other.