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6 CONCERNING BEING AND ESSENCE substances and secondarily and as if in a certain respect (secundum quid) of accidents, hence it is that essence also exists truly and properly in substances, but exists in accidents in a certain mode and in a certain respect. Some substances indeed are simple and others are composite, and in both there is an essence. But essence is possessed by simple substances in a truer and more noble mode according as simple substances have a more exalted existence, for they are the cause of those which are composite, at least the primary substance, which is God, is. But since the essences of these substances are more concealed from us, therefore we must begin from the essences of composite substances in order that instruction may be made more suitably from what is easier.