This chapter discusses the analogy between bare possibles and imaginary numbers, developed by Leibniz during his Paris years. In this period, he came to realize that imaginary quantities are not impossible in themselves, but they cannot be geometrically represented, for they cannot be ordered within the number line. Similarly, he regarded actual things as belonging to a single ‘series of things’, where each member is connected to every other by relations of position and succession. Bare possibles, on the contrary, can be placed nowhere in the series and, therefore, must be regarded as fictions (though reference to them is in a sense unavoidable, like the use of imaginary quantities in algebra). The young Leibniz does not extend the model of a ‘series of things’ to possibles, thus in this period he seems to reject the very idea of a plurality of possible worlds.