Spinoza did not, however, choose the geometrical order because he thought his philosophy too profound for ordinary exposition; nor did he choose it because he was enmeshed in medieval philosophic speculation. He chose it because his fundamental philosophic aim was to establish ethics on a thoroughly tested, scientific foundation; and geometry, an exemplar of all mathematical science, most completely embodied, at that time, the highest scientific ideal. Man, Spinoza held, is a part of Nature, and Nature is governed by eternal and immutable laws. It must be just as possible, therefore, to apply the mathematical method to man, as it is to apply it to matter. It must be possible to determine, with the certitude obtainable in the exact sciences, what things are good for man and what means he has for attaining them. Spinoza's belief in the self-sufficing, lawful order of Nature, and the adequacy of the natural powers of our mind to understand the mysteries (popularly so appraised) of heaven and earth, the singular expository style of the _Ethics_ emphasizes in unmistakable fashion. Even for our understanding of God's own nature, Divine Revelation, as commonly interpreted in Spinoza's day and our own, is wholly unnecessary. We need only the revelation afforded by the natural powers of reason operative in us. In geometry, we do not blindly accept conclusions on faith, nor do we reject them by authority. We are guided in our discovery of the true and the false, solely by the light of our natural understanding. And the truths we discover are not temporary fabrications of the human mind, but eternal truths about the nature of things. Perhaps no other single aspect of Spinoza's philosophy distinguishes Spinoza from the medievalists as thoroughly as does his use of the geometrical order of exposition; and no other single aspect, perhaps, justifies as thoroughly Spinoza's claim to rank with the moderns if not even the contemporaries.