Aquinas's use of the related concepts of reason and law therefore made it possible for him to regard man's perfection as something towards which his own rational nature necessarily tended, rather than as something to be achieved in accordance with norms discoverable only by recourse to revelation or authority and anyway extrinsic to the internal exigencies of human moral aspiration and rational experience. There were limits in the extent to which Aquinas took this conclusion. He would not, for instance, concede that while it was certainly wrong to act against an erroneous judgement of conscience, it was therefore necessarily right to follow it. He argued against the necessity of invincible error in a world in which he thought everyone came into contact with the gospel message. But the implication that man's perfection was by and large to be achieved in accordance with the moral aspirations with which his rational nature endowed him was a clear and important step forward from Augustine towards a more humane moral and theological system.