Note.---Mr. Stephen (Science of Ethics, chap. v. §33) explains the exceptions to the rule of truth-speaking as follows:---
``The rule, `Lie not', is the external rule, and corresponds approximately to the internal rule, `Be trustworthy'. Cases occur where the rules diverge, and in such cases it is the internal rule which is morally approved. Truthfulness is the rule because in the vast majority of cases we trust a man in so far as he speaks the truth; in the exceptional cases, the mutual confidence would be violated when the truth, not when the lie, is spoken.''
This explanation seems to me for several reasons inadequate. (1) if we may sometimes lie to defend the life or secrets of others, it is para doxical to say that we may not do so to defend our own; but a falsehood in self-defence obviously cannot be justified as an application of the maxim ``be trustworthy''. (2) Even when the falsehood is in legitimate defence of others against attacks, we cannot say that the speaker manifests ``trustworthiness'' without qualification; for the deceived assailant trusts his veracity, otherwise he would not be deceived: the question therefore is under what circumstances the confidence of A that I shall speak the truth may legitimately be disappointed in order not to disappoint the confidence of B that I shall defend his life and honour. This question Mr. Stephen's explanation does not in any way aid us to answer.
The general question raised by Mr. Stephen, as to the value of ``internal rules'', expressed in the form ``Be this'', in contrast to external rules, expressed in the form ``Do this'', will be dealt with in a subsequent chapter (xiv. §1).ME Book 3 Chapter 7 Section 3