Universally then, according to St. Paul, two sources of the knowledge of God exist; nature, with its evidences of the divine power and other similar attributes, and conscience, with its witness to divine righteousness. And, though the sciences of nature and man have grown since St. Paul's day past recognition, nothing (we may boldly say) has really weakened either element of this double witness. It is, and remains true, that the only reasonable argument from the universal order of nature is to a universal reason or mind: and that the method by which the moral conscience may be believed to have developed out of 'animal intelligence,' makes no difference as to the cogency of its witness to a divine righteousness, in response to which alone it could have developed as in fact it has done. It is worth notice also before we leave this part of our subject, that St. Paul's line of thought affords a true explanation of the double fact that, on the one hand, the actual moral standards with which the conscience of different individuals, races, and generations is satisfied, greatly varies; and, on the other hand, that all the standards tend towards unity in a common idea of righteousness. The tendency towards unity St. Paul would attribute to the divine righteousness {106} which lies behind conscience and which it exists to reflect. The variations would be due to the different degrees of development reached; or still more to the different degrees of faithfulness or unfaithfulness, attention or inattention, with which the conscience of the race or the individual has responded to the light. The conscience, like the speculative reason, is an instrument for coming to the truth; but an instrument capable of every variety of racial or individual error or obtuseness.