Now we do not call the operation of these causes _absolutely_ certain, because they depend ultimately upon will,--the will of God; and we can conceive that the same will which ordained them, can change, suspend, or even annihilate them: they have no intrinsic necessity, still, as causes given in time and space, we conceive of them generally as immutable. If in any case they be changed, or suspended, we are compelled to recognise the presence of that will which ordained them. Such change or suspension we call a _miracle_; that is, a surprise,--a wonder, because it is unlooked for. When, therefore, we affirm any thing to be physically certain, we mean that it is certain in the immutability of a cause acting in time and space, and under a necessity relatively to the divine will; but still not _absolutely_ certain, because there is a possibility of a miracle. But when we affirm any thing to be absolutely certain, we mean that it is certain as comprehended in a principle which is unalterable in its very nature, and is therefore independent of will. _Thirdly_. Moral certainty, is the certainty which lies between the connexion of motive and will. By will we mean a self-conscious and intelligent cause, or a cause in unity with intelligence. It is also, in the fullest sense, a cause _per se_; that is, it contains within itself proper efficiency, and determines its own direction. By _motives_ we mean the reasons according to which the will acts. In general, all activity proceeds according to rules, or laws, or reasons; for they have the same meaning: but in mere material masses, the rule is not contemplated by the acting force,--it is contemplated only by the intelligence which ordained and conditioned the force. In spirit, on the contrary, the activity which we call will is self-conscious, and is connected with a perception of the reasons, or ends, or motives of action. These motives or ends of action are of two kinds. _First_, those found in the ideas of the practical reason, which decides what is fit and right. These are reasons of supreme authority. _Secondly_, those found in the understanding and sensitivity: e. g. the immediately useful and expedient, and the gratification of passion. These are right only when subordinate to the first. Now these reasons and motives are a light to the will, and serve to direct its activities; and the human conscience, which is but the reason, has drawn up for the will explicit rules, suited to all circumstances and relations, which are called _ethics_, or _the rules_.