The main points of the exposition are: (i) For all conjunctions, a common topic is necessary; if it is not overtly present, it must be possible to deduce it from the presuppositions. (ii) There is a hierarchy of naturalness of the presuppositions and deductions; the more widespread or natural the presupposition, the more likely it is that the conjunction itself will be accepted by the hearer. (iii) Coordinate conjunctions have symmetric and asymmetric uses; in an asymmetric conjunction, the first element is presupposed in order for the second to be true.