“In this it is implied,” says Descartes, “that thought is more certain to me than body. If from the fact that I touch or see the earth I judge that it exists, I must more certainly judge from this that my thought exists. For it may very well happen that I judge the earth to exist, even if it does not exist, but it cannot be that I judge this, and that my mind which judges this does not exist.”[163] That is to say, everything which is for me I may assert to be non-existent, but when I assert myself to be non-existent, I myself _assert_, or it is _my_ judgment. For I cannot set aside the fact that I judge, even if I can abstract from that respecting which I judge. In this Philosophy has regained its own ground that thought starts from thought as what is certain in itself, and not from something external, not from something given, not from an authority, but directly from the freedom that is contained in the ‘I think.’ Of all else I may doubt, of the existence of bodily things, of my body itself; or this certainty does not possess immediacy in itself. For ‘I’ is just certainty itself, but in all else this certainty is only predicate; my body is certain to _me_, it is not this certainty itself.[164] As against the certainty we feel of having a body, Descartes adduces the empirical phenomenon that we often hear of persons imagining they feel pain in a limb which they have lost long ago.[165] What is actual, he says is a substance, the soul is a thinking substance; it is thus for itself, separate from all external material things and independent. That it is thinking is evident from its nature: it would think and exist even if no material things were present; the soul can hence know itself more easily than its body.[166] All else that we can hold as true rests on this certainty; for in order that anything should be held as true, evidence is requisite, but nothing is true which has not this inward evidence in consciousness. “Now the evidence of everything rests upon our perceiving it as clearly and vividly as that certainty itself, and on its so entirely depending from, and harmonizing with this principle, that if we wished to doubt it we should also have to doubt this principle likewise” (our _ego_).[167] This knowledge is indeed on its own account perfect evidence, but it is not yet the truth, or if we take that Being as truth, it is an empty content, and it is with the content that we have to do.