In this case, the borrowing would not take place.
William would be bound either to make a plane for himself, or to do without one, which would leave him in his original condition.

He borrows, because he gains by borrowing.

I know very well what will be told me.

You will say, William may be deceived, or, perhaps, he may be governed by necessity, and be obliged to submit to a harsh law.
It may be so.

As to errors in calculation, they belong to the infirmity of our nature, and to argue from this against the transaction in question, is objecting the possibility of loss in all imaginable transactions, in every human act.