Baruch Spinoza

That thing is called free, which exists solely by the necessity of its own nature, and of which the action is determined by itself alone. On the other hand, that thing is necessary, or rather constrained, which is determined by something external to itself to a fixed and definite method of existence or action.

Everything which exists, exists either in itself or in something else.

That which cannot be conceived through anything else must be conceived through itself.

Things which have nothing in common cannot be understood,

Things which have nothing in common cannot be understood,