DEPARTMENT OF PHILOSOPHY
University of Toronto at Mississauga
PHL105Y5: Introduction to Philosophy
The Principle of Sufficient Reason
There must be an explanation (a) of the existence of any being and (b)
of any positive fact whatever.
PSR, Version 1:!There is an explanation for every positive fact.
PSR, Version 2:!Whatever exists must have an explanation of its existence!either in the necessity of its own
nature or in the causal efficacy of some other being.
PSR, Version 3:!Whatever comes into existence must have an explanation of its existence in the causal
efficacy of some other being.
Nothing can be more absurd, than to suppose that anything (or any circumstance of thing) is; and yet that
there be absolutely no reason why it is, rather than not. 'Tis easy to conceive, that we may be utterly ignorant
of the reasons, or grounds, or causes of many things. But, that anything is; and that there is a real reason in
nature why it is, rather than not; these two are as necessarily and essentially connected, as any two correlates
whatever, as height and depth, etc.
!Samuel Clarke, Letter
The separation, therefore, of the idea of a cause from that of a beginning of existence is plainly pos