To keep them on the threshold of hope is diplomatic; to trust to their gratitude is boorish; hope has a good memory, gratitude a bad one"?
There is much more of this kind; but after the assurance that only a boorish person (that is to say, an ignorant and vulgar man) can believe in gratitude, the author's opinion of human nature needs no further elucidation.

The old Norseman would have been shocked at such a statement.

But he might have approved the following: "When you hear anything favourable, keep a tight rein upon your credulity; if unfavourable, give it the spur." That is to say, when you hear anything good about another man, do not be ready to believe it; but if you hear anything bad about him, believe as much of it as you can.
I notice also many other points of resemblance between the Northern and the Spanish teaching in regard to caution.

The "Havamal" says that you must not pick a quarrel with a worse man than yourself; "because the better man often falls by the worse man's sword." The Spanish priest gives a still shrewder reason for the same policy.

"Never contend," he says, "with a man who has nothing to lose; for thereby you enter into an unequal conflict.