Full Idea
Whatever agrees with the formal conditions of experience is possible, ...and that whose connection with the actual is determined in accordance with general conditions of experience is (exists) necessarily.
Gist of Idea
Formal experience conditions show what is possible, and general conditions what is necessary
Source
Immanuel Kant (Critique of Pure Reason [1781], B266/A218)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.321
A Reaction
This is the Kantian view of necessity, as more concerned with how we think than with how the world is. I think there are necessities in reality, and philosophy endeavours to discern what they are (despite the mockery of scientists).
Related Idea
Idea 18795 A concept is logically possible if non-contradictory (but may not be actually possible) [Kant]