While rejecting some of Luther's explanations, Calvin was undoubtedly nearer his position than that of Zwingli, which he characterized as "profane." As few instructed and thinking persons now accept the conclusions of the _Institutes_, it is natural to underestimate the power that they exercised in their own day.

This book was the most effective weapon of Protestantism.

This was partly because of the style, but, still more because of the faultless logic.

[Sidenote: His logic] The success of an argument usually depends far less on the truth of the premises than on the validity of the reasoning.

And the premises selected by Calvin not only seemed natural to a large body of educated European opinion of his time, but were such that their truth or falsity was very difficult to demonstrate convincingly.