Analyzing the process of keeping promise we identify its sequence structure and its phase sequences in time. This allows us to arrive at a time order principle forming according to which obligation performance cannot precede in time its sufficient or necessary conditions performance. We further observe that a given promise must always be taken as an element of a certain system of promises. As a result we review definitions of the terms sufficient condition and necessary condition as no more allowing their mutual defining, or symmetry (conversion). We try to discover the compliance rules concerning the condition – the conditioned vector, the course of events vector and the time vector. We conclude that it indicates an incorrect use if, provided the condition – the conditioned vector complies with the course of events vector, the negative time difference in the descriptive use of sentences involving either the if-then connective or the only if connective is obtained. Only when using sentences for abductive explanation with a dominating epistemic vector the negative difference of time does not indicate erroneous use; however, this is possible only for the term of sufficient condition. We further suggest reviewed definition generalization involving the terms of sufficient condition and necessary condition containing always a parameter element denot-ing a given modality type, or a particular system of rules, laws, etc. Such definition satisfies Brennan’s requirement of a “general formal scheme” where the notion of sufficient condition and necessary condition symmetry (conversion) does not apply.
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