But I frankly recognize that this is not to explain the difficulty and that, leaving the preoccupations and illusions of my senses, I would be wrong to resort to an abstract form and to embrace a phantom of logic as the cause I see; I mean that I would be wrong to conceive the vague idea of nature or essence, which expresses only what is known, as something real and distinct, and thus to take an abstract and universal form as a physical cause of a very real effect.