 In his 2010 book, Yagisawa is more distant from Lewisian modal realism. He still admits impossible worlds and impossibilia, and he rejects ersatz accounts of them. However, he now takes worlds to be points in modal space. Worlds are modal indices for truth, just like times are temporal indices for it; and modal matters are treated in a way similar to how four-dimensionalist philosophers, who believe in  temporal parts,  treat temporal matters. According to four-dimensionalists, material objects are like temporal worms extended across time: an object has a property at time \(t\) by having a temporal stage at time \(t\) which has that property. Analogously, for Yagisawa an object has a modal property, a property at world \(w\), by having a modal stage at world \(w\) which has that property.