First law of Commonsense -

 First law of Commonsense - 

Something is "allowed" if it is LIKE something else which is allowed.

Consider this piece of commonsense knowledge - Roads cannot fly.

Now I ask you - why cannot roads fly? One response would be that they don't have wings to fly. 

Then I would say - even human beings fly; we say "I flew to New York ''.

Then you would say - well, then they would need to be carried in an airplane like humans are. 

I would say - carry them.

Then you would say - well, then they would have to be cut/sliced from the earth/ground. Then that sheet would have to be placed on the floor of a big airplane and flown.

Now, notice what you have done at every stage. First, you said - they don't have wings. Then you said they would need to be carried in an airplane like humans are. And then you said they would need to be sliced and then placed on the floor of a big airplane to be flown. At every stage, you have LIKENED the road to something else in whose case the possibility of the proposition was knowingly allowed. First to a bird, then to being carried in an airplane like humans are, and then sliced like, say, a layer of cream from cake and then to something like cargo being placed on the floor of an airplane for them to be "flown". 

(You have never considered the road, just on its own, as to be able to be done with those propositions on, so to speak).

This is how commonsense thinking works - you liken a new proposition to something else in whose case the proposition is valid/allowable. In one way, this would seem obvious, because ultimately the proposition is something "in the external world" which is "coming at you" and all you have to "deal with it" is your brain, in which is stored valid knowledge, with whose elements you liken the constituents of the proposition, for considering the latter's allowability/possibility. 

We automatically seek recourse in whose evidence/knowledge we have already.