The "order of facts" in the subject of morality requires precisely similar mental treatment to those to which scientific investigation has been already applied with such great success, and which include all phenomena admitting of observation, comparison, analysis and inference; and not only those in which we are able, but also those in which we are not able to produce by means of experiment, the phenomena to be observed, such as those of astronomy and geology. Different subjects also are experimental in different degrees, physical science is more experimental, physiology is more observational; morality is partly experimental, and therefore capable of reduction to scientific system by means of our intellectual powers. In consequence of the essential nature of truth being the same in all subjects, and of the fundamental processes of mental action in the determination of truth being also alike in all, the essential modes of arriving at and detecting moral truth are the same as those employed in research in the physical sciences. We possess therefore no special faculty, call it "conscience," or what we may, by which we are enabled to infallibly arrive at truth in moral questions. What is right and good, and what is wrong and evil, are determined by precisely the same general means as what is true; our much vaunted consciousness alone does not infallibly tell us; reason alone, {127} acting upon the evidence, is the final arbiter in any doubtful or disputed case. The truth of moral questions must be examined and tested by precisely the same mental faculties and processes as those employed in physical science, viz:--by the faculties of perception, observation, comparison, and inference, acting upon the whole of the evidence; and by the processes of observing facts, comparing them, inferring conclusions; by analysing and cross-examining the evidence in every possible way, and extracting from it the largest amount of consistent knowledge.