 It should be noted that finding an adequate definition of abstract objects is a matter of considerable controversy. According to a common view, abstract entities lack spatio-temporal properties and relations, as opposed to concrete objects which exist in space and time (Lowe 1995: 515). In this respect truth values obviously are abstract as they clearly have nothing to do with physical spacetime. In a similar fashion truth values fulfill another requirement often imposed upon abstract objects, namely the one of a causal inefficacy (see, e.g., Grossmann 1992: 7). Here again, truth values are very much like numbers and geometrical figures: they have no causal power and make nothing happen.