Matter and mind are as heat and cold, as life and death, certainty and uncertainty, union and separateness.
 Samuel Butler, The Note-Books of Samuel Butler (1912). copy citation

Context

“Perhaps we surreptitiously introduce some little attribute, and then we think we have conceived of matter pure and simple, but this I think is as far as we can go. The like holds good for mind: we must smuggle in a little matter before we get any definite idea at all. ii Matter and mind are as heat and cold, as life and death, certainty and uncertainty, union and separateness. There is no absolute heat, life, certainty, union, nor is there any absolute cold, death, uncertainty or separateness. We can conceive of no ultimate limit beyond which a thing cannot become either hotter or colder, there is no limit;” source