Renan agreed with Browning in this estimate of his intelligence, and made him the foundation of a philosophical play.
There is some slight reason for this in Shakespeare's invention.

He lifts Caliban in intellect, even in feeling, far above Trinculo, Stephano, the Boatswain and the rest of the common men.

The objection, however, has been made that Browning makes him too intelligent.

The answer is that Browning is not drawing Caliban only, but embodying in an imagined personage the thoughts about God likely to be invented by early man during thousands of years--and this accounts for the insequences in Caliban's thinking.

They are not the thoughts of one but of several men.
Yet a certain poetic unity is given to them by the unity of place.