The friends of Mars, who cannot bear the prospect of perpetual peace, maintain that war is an indispensable instrument of Progress.

It is in the name of Progress that the doctrinaires who established the present reign of terror in Russia profess to act.

All this shows the prevalent feeling that a social or political theory or programme is hardly tenable if it cannot claim that it harmonises with this controlling idea.
In the Middle Ages Europeans followed a different guiding star.

The idea of a life beyond the grave was in control, and the great things of this life were conducted with reference to the next.

When men's deepest feelings reacted more steadily and powerfully to the idea of saving their souls than to any other, harmony with this idea was the test by which the opportuneness of social theories and institutions was judged.
Monasticism, for instance, throve under its aegis, while liberty of conscience had no chance.