Properties as set of individuals, or of features? Worlds, or propositions? Time-points, or events? Preference, or choice? Natural kinds, or similarity? In modern analytic philosophy it is standard to take (i) individuals as basic, and properties as defined in terms of them; (ii) worlds as basic, and propositions as defined in terms of them; (iii) time-points as basic, and intervals as constructions out of them; (iv) preference as basic, and optimal choice as defined in terms of them; and (v) natural kinds as basic, and similarities as defined in terms of them. In this chapter we show that in all cases the other direction is possible as well. Most of the constructions used are well-known. But by putting them collectively on the table we hope to show that the constructions have something in common, and that it is not always clear which perspective is ontologically less committing.