To my surprise, however, I found that that single, simple principle does, in fact, exist.

We have no law but the single principle of mutual aid between individuals.

We have no government but the single principle of free association.

That single principle helped to unify the whole field of physics.

Nor is it the working out of a single guiding principle through all areas of life.

Either you're a liar or a man without a single principle.

The failure to execute a single principle may render the others less effective.

Second, the classification does not seem to obey any single, logical principle.

Surely that single principle is one which must cross all party boundaries?

But mostly they have promoted a single principle: profit-seeking companies should stay out of public education.