How do we determine which part of the statement is X or Y if:

X --> Y

For example, why is it :

microscopic organism → capable of feeling pain

and NOT

capable of feeling pain --> microscopic organism

Philadelphia → sunny

/sunny → /Philadelphia

Therefore,

(1)philadelphia is always sunny

(2) If its not sunny, its not in Philadelphia

even though 2 is factually incorrect, is this the right way to go about it? please help