 Abelard holds that two things are the same in essence when they are numerically the same concrete thing (essentia), and essentially different otherwise. The Morning Star is essentially the same as the Evening Star, for instance, since each is the selfsame planet Venus. Again, the formal elements that constitute a concrete thing are essentially the same as one another and essentially the same as the concrete thing of which they are the formal constituents: Socrates is his essence (Socrates is what it is to be Socrates). The corresponding general thesis does not hold for parts, however. Abelard maintains that the part is essentially different from the integral whole of which it is a part, reasoning that a given part is completely contained, along with other parts, in the whole, and so is less than the quantity of the whole.