There’s an old story about two men on a train. One of them, seeing some naked-looking sheep in a field, said, “Those sheep have just been sheared.’; The other looked a moment longer, and then said, “They seem to be— on this side.” It is in such a cautious spirit that we should say whatever we have to say about the workings of the mind.

Two Englishmen are going by train. A conversation isn’t getting on. The train passes a meadow, on which a herd of sheeps pastures. One of the passengers says:

—1356.

The other man is surprised, but gives no answer. In some time the train passes another pasture. The first passenger says:

—1693.

His neighbor brakes and asks:

—Sir, our train moves at speed 60 miles per hour. How can you count so quickly?

—Oh, sir, it’s very simple! First I count a quantity of legs in a herd and then I divide this number by four.