‘Behold, the ships also, though they are so great and are driven by rough winds, are yet turned about by a very small rudder, wherever the will of the steersman directs.'
The thought of ‘turning about' now brings to mind a second illustration and that is of a steersman steering a ship. He has but a small rudder, but with such a small rudder a good steersman can make the large ship do precisely what he wants, even when being driven by rough winds (that is, by what a landlubber like James thought were rough winds). So in spite of the largeness of the ship, and the fierceness of the winds, the small rudder is still able to control it.
His point is that the church too is large, and faces fierce storms, but if those who exercise authority in teaching do so wisely the whole church will move forward in the direction in which God wants it to go. But let their teaching once become marred, then the church will begin to suffer and begin to find itself at the mercy of wind and storm.