Adam  Smith  had an  elegant  summary  connecting the argument for trade to that for international trade:
It is the maxim of every prudent master of a family never to attempt to make at home what it will cost him more to make than to buy. The tailor does not attempt to make his own shoes,  but buys them of the shoemaker. The shoemaker does not attempt to make his own clothes,  but employs a tailor. What is prudence in the conduct of every private family can scarce be folly in that of a great kingdom.  If a foreign country can supply us with a commodity  cheaper than  we ourselves can make  it,  better  buy it of them with  some  part  of  the  produce  of  our  own  industry  employed  in  a  way  in which we have some advantage.