Oh, I don't think you have to say any other word when you know him. If you don't know him you might have to say more than one word. And it's hard to know where to begin. It could be energy. He was very interested in energy himself and liked multiplying it with synergy to bring about greater energies than we had imagined simply by putting two things together that then brought about a mysterious other power.
Energy is certainly one of the things, and the other is optimism.
And solving, I don't know, solving all the problems, even those which we are not aware of. Realizing that there could be problems that we're not aware of and that if we make our solutions radically enough that they will have solved those problems even though we don't know them, I think. And his confidence cut through, say, the absence of information. Not on his part, but if on anyone's part who didn't have all, all the facts at hand. Bucky thought the important thing about his work was that it existed in book form, in the idea form and that the seeds of it were both planted and distributed throughout the earth.