Sara Bernstein

In "Changing the Past" (2010), Peter van Inwagen argues that a time traveler can change the past without paradox in a growing block universe. After erasing the portion of past existence that generates paradox, a new, non-paradox-generating block can be "grown" after the temporal relocation of the time traveler. I articulate and explore the underlying mechanism of Van Inwagen's model: the time traveler's control over the location of the objective present. Van Inwagen's model is aimed at preventing paradox by changing the past, but it achieves something broader than paradox avoidance: it gives tools for a new model of time travel. I use van Inwagen's tools to develop a new kind of time travel in which in which the location of the objective present is shifted by the time traveler. I call this type of time travel Movable Objective Present, or MOP. After defining MOP, I argue that it is compatible with any theory of time that accepts hypertime, including presentism and moving spotlight theory.

Theories of causation grounded in counterfactual dependence face the problem of profligate omissions: numerous irrelevant omissions count as causes of an outcome. A recent purported solution to this problem is proportionality, which selects one omission among many candidates as the cause of an outcome. This paper argues that proportionality cannot solve the problem of profligate omissions for two reasons. First: the determinate/determinable relationship that holds between properties like aqua and blue does not hold between negative properties like not aqua and not blue. Negative properties are those at stake in omissive causation. Second: proportionality misconstrues the nature of the problem to be solved.