SHOULD AND WOULD

170. Should and would are the past-time forms of shall and will. We use them to express action or existence dependent upon some condition, thus:

I should go if I were well enough.
He should join us if you asked him.

In these sentences should and would express action which is possible now or will be in the future, provided some other action takes place.

The same distinction which we found made in the use shall and will has been made with should and would; that is, that should used with the first person, expresses action dependent upon condition; but would, used with the first person, implies exercise of the will. This rule is not closely followed, though it expresses a nice distinction in the use of should and would. In ordinary usage we use either should or would with the first person without any distinction of meaning, as for example:

I should struggle on even if it meant death.
I would stand for my principles though I stood entirely alone.

We do not use should however, with the second and third persons to express an action or existence dependent upon some condition. Should used with the second and third person implies obligation. Would is used with the second or third person to express an action dependent upon some condition, as for example:

He would not go, even if you insisted.
They would come if you invited them.
You would believe him if you could hear him.
You would be surprised if I should tell you the reason.

171. Should and would in all of the sentences which we have quoted are used to express action or existence dependent upon some condition which is expressed in that part of the sentence introduced by such conjunctions as if and though.

The parts of the sentence introduced by these conjunctions express the condition upon which the other action is dependent. When we use should in sentences without this condition, it means practically the same as ought, and implies an obligation. We use should with the first and second and third persons when we use it with this meaning, as for example:

I should have gone yesterday. You should be with us in this fight. They should never fear defeat.

172. Ought could be used in all these sentences and express practically the same meaning. Should used in this way implies obligation.