; whether there is any where, perhaps in my thinking self, an indivisible and indestructible unity, or whether there is nothing but that which is divisible and per ishable; whether my actions are free or, like those of other beings, con trolled by the strings of nature and fate; whether, finally, there is a supreme cause of the world, or whether natural things and their order constitute the ultimate object, at which all our consideration of things must stop these are questions for whose solution the mathematician would gladly give up his entire science;