Pass, now, to Mr. Spencer's "Principles of Morality"; and although but one volume of this work has been as yet published, we may see that he is entirely consistent with what he has said in his "Sociology" and his other writings.[127] He does not leave us in any doubt as to his theory of morals. It appears, from the preface to his "Data of Ethics," that he has been compelled by ill-health to deviate from the plan which he had mapped out for himself, and to publish one volume of his "Principles of Morality" before completing his "Principles of Sociology." But while we have reason for his sake and for the sake of the world to regret this, we can easily understand his system of morality. He means to rest the rules of right conduct on a scientific basis, and he shows that this is a pressing need. In his preface, he says: I am the more anxious to indicate in outline, if I can not complete, this final proof, because the establishment of rules of right conduct on a scientific basis is a pressing need. Now that moral injunctions are losing the authority given by their supposed sacred origin, the secularization of morals is becoming imperative. Few things can happen more disastrous than the decay and death of a regulative system no longer fit, before another and fitter regulative system has grown up to replace it. Most of those who reject the current creed appear to assume that the controlling agency furnished by it may be safely thrown aside, and the vacancy left unfilled by any other controlling agency. Meanwhile, those who defend the current creed allege that, in the absence of the guidance it yields, no guidance can exist; divine commandments they think the only possible guides. Thus, between these extreme opponents there is a certain community. The one holds that the gap left by disappearance of the code of supernatural ethics need not be filled by a code of natural ethics; and the other holds that it can not be so filled. Both contemplate a vacuum, which the one wishes and the other fears. As the change which promises or threatens to bring about this state, desired or dreaded, is rapidly progressing, those who believe that the vacuum can be filled are called upon to do something in pursuance of their belief.