Mathematics brought rigor to Economics. Unfortunately, it also brought mortis.

A somewhat casual observer from outer space might well deduce that the course of evolution in this planet had produced a species of large four-wheeled bugs with detachable brains; peculiar animals which rested when they sent their brains away from them but performed in rather predictable manner when their brains were recalled.

Economics, we learn in the history of thought, only became a science by escaping from the casuistry and moralizing of medieval thought.

Thus we seem to be on the verge of an expansion of welfare economics into something like a social science of ethics and politics: what was intended to be a mere porch to ethics is either the whole house or nothing at all. In so laying down its life welfare economics may be able to contribute some of its insights and analytical methods to a much broader evaluative analysis of the whole social process.

The discounting presumably is to be done for each period of time at that rate of interest which represents the alternative cost of employing capital in the occupation in question; that is, at the rate which the entrepreneur could obtain in other investments

It is clear that the building of models is not a purely mechanical process but requires skill of a high order - not merely mathematical skill but a sensitivity to the relative importance of different factors and a critical, almost an artistic, faculty in the selection of behaviour equations which are reasonable, tentative hypotheses in explaining the behaviour of actual economies.

If we saw tomorrow's newspaper today, tomorrow would never happen.