 The Stoic conception of philosophy, therefore, was often far more suitable to a classroom situation. For the Stoics, the universe was rationally organized in a way that was directly equivalent to human reason. They believed that there was a correspondence in the universe, or in nature, between order and reason and that the reason which organized and governed the universe was essentially the same as human reason. The connection between nature and reason could be studied from three different perspectives: physical, ethical and rational or logical. One consequence of the Stoic theory was that there must be an absolute analogy between the contents of an art and those of nature, that is, all arts must also be about nature or being. There could not be a difference of rank between the parts of nature, nor between the parts of philosophy, as the Aristotelians thought. Another consequence was that logic became an integral part of philosophy rather than an instrument to be used by the other branches of the discipline.