1. Besides printing, many methods are now in vogue for multiplying copies of a document. Commonly the document is written out with special ink on special paper: the copy thus used is called a _stencil_; and from it other copies are struck off. We will suppose the stencil to be that page of the Eternal Law written in the Mind of God, which regulates _human acts_, technically so called. The copies struck off from that stencil will be the Natural Law in the mind of this man and of that. Now, as all who are familiar with copying processes know too well, it happens at times that a copy comes out very faint, and in parts not at all. These faint and partial copies represent the Natural Law as it is imperfectly developed in the minds of many men. In this sense, and as we may say _subjectively_, the Natural Law is mutable, very mutable indeed. Still, as no one would say that the document had been altered, because some copies of it were bad, so it is not strictly correct to say that the Natural Law varies with these subjective varieties. Appeal would be made to a full and perfectly printed impression of the document, one that rendered the stencil exactly. The Natural Law must be viewed in like manner, as it would exist in a mind perfectly enlightened concerning the whole duty of man, and exactly reproducing in itself that portion of the Eternal Law which ordains such duty. Were such a mind to discern a natural obligation to lie differently at two different times, all the relevant circumstances being alike in both cases, and the moral solution different, then only could the Natural Law be held to have changed. 2. But this is clearly impossible. The conclusion of a geometrical theorem is a truth for all time. There is no difference here between a complicated theorem, having many conditions, and a simpler theorem with fewer. It is indeed easier for a few than for many conditions to be all present together: but the enunciation of the conclusion supposes _all_ the conditions, whatever their number. The same in a practical manner, as in the stability of a bridge. The bridge that would stand in England, would stand in Ceylon. If it would not, there must have occurred some change in the conditions, as the heat of the tropical sun upon the girders. A point of casuistry also, however knotty, once determined, is determined for ever and aye, for the circumstances under which it was determined. The Natural Law in this sense is absolutely immutable, no less in each particular application than in the most general principles. We must uniformly pass the same judgment on the same case. What is once right and reasonable, is always right and reasonable, in the same matter. Where to-day there is only one right course, there cannot to-morrow be two, unless circumstances have altered. The Natural Law is thus far immutable, every jot and tittle.