Time and Persistence

x is a temporal part of y during t =df (i) x is part of y during t, (ii) x overlaps everything that’s a part of y during t, and (iii) x exists only during t. Perdurantism: Objects persist through time by having different temporal parts at different times.

…what is unique is always homogeneous with itself, and what is homogeneous can neither perish nor grow nor change its arrangement nor suffer pain nor suffer anguish. For if it underwent any of these things it would not be homogeneous. For anything that undergoes any change of whatever sort moves from one state into a different one. But nothing is different from what exists. Therefore it will not change.

Melissus, quoted by Simplicius in Commentary on the Physics

The Problem of Change

1) If the banana changes, then the old banana must be numerically identical to the young banana.

2) If the banana changes, then the old banana and the young banana must have different properties.

3) For any x and y, if x is numerically identical to y, then x and y must have all the same properties.

4) The banana does not change.5) Nothing changes.

The bad but tempting objection is that perdurance theory cannot account for change, because according to perdurance theory nothing really changes. According to perdurance theory, things ‘change’ by having a succession of different temporal parts with different properties. The objection is that, by definition, change consists in one and the same object having different properties as different times, not a succession of different things with different properties.

Katherine Hawley

Let us consider the case of another sort of series. The meridian of Greenwich passes through a series of degrees of latitude. And we can find two points in this series, S and S', such that the proposition “At S the meridian of Greenwich is within the United Kingdom” is true, while the proposition “At S' the meridian of Greenwich is within the United Kingdom” is false. But no one would say that this gave us change. Why should we say so in the case of the other series?

JME McTaggart