He had merely seized upon the first excuse which presented itself for ending all, because he was in reality past hope.
We have, as yet, no absolute test of sanity, as we have of fever in the body and of many other unnatural conditions of the human organism.
The only approximately accurate judgments in the patient's favour are obtained from examinations into the relative consecutiveness and consistency of thought in the individual examined, when the whole tendency of that thought is towards an end conceivably approvable by a majority of men.

A great many philosophers and thinkers have accordingly been pronounced insane at one period of history and have been held up as models of sanity at another.

The most immediately destructive consequences of individual reasoning on a limited scale, murder and suicide, have been successively regarded as heroic acts, as criminal deeds, and as the deplorable but explicable actions of irresponsible beings in consecutive ages of violence, strict law and humanitarianism.
It seems to be believed that the combination of murder and suicide is more commonly observed under the last of the three reigns than it was under the first; it was undoubtedly least common under the second.

In other words it appears probable that the practice of considering certain crimes as the result of insanity has a tendency to make those crimes increase in number, as they undoubtedly increase in barbarity, from year to year.

Meanwhile, however, no definite conclusion has been reached as to the state of mind of a man who murders the woman he loves and then ends his own life.
Israel Kafka may therefore be regarded as mad or sane.