The proof of this is that they were willing to transact business with him.
Obviously they were; since it is then that the offer of chartering his ship for the special purpose of proceeding to the Western Islands was put in his way by a firm of shipbrokers who had no doubt of his sanity.
He probably looked sane enough for all the practical purposes of commercial life.

But I am not so certain that he really was quite sane at that time.
However, he jumped at the offer.

Providence itself was offering him this opportunity to accustom the girl to sea-life by a comparatively short trip.

This was the time when everything that happened, everything he heard, casual words, unrelated phrases, seemed a provocation or an encouragement, confirmed him in his resolution.

And indeed to be busy with material affairs is the best preservative against reflection, fears, doubts--all these things which stand in the way of achievement.