of sharing the product or its price when produced. We can then imagine Robinson Crusoe on his island fishing off the rocks with a string and a hook and a bait, with more or less success, for the fish which come inshore. He then comes to the conclusion that it will be worth while for him, in order to fish more easily and quickly, to build himself a boat; but first of all he has to consider whether the work which he will put into making the boat might not be better applied to tilling his land, and so improving its output of cereals, or into improving his bows and arrows, or any other weapons with which he goes hunting, or whether it would not on the whole be better to continue to go on as he is, and trust to the variation of his diet by the simple method of fishing off the rocks as he has done before. In other words, he has to consider whether the time and work that he is going to put into the project will repay him, whether the boat which he is going to try to build is likely to be seaworthy, and whether it will really be true that by going a little further away from the shore he will be able to increase materially his power to catch fish.
If he decides that on the whole it is worth while to carry out his design, he will have to
