We consider the possibility that there may be causality violation detectable
at higher energies. We take a scalar nonlocal theory containing a mass scale
Λ as a model example and make a preliminary study of how the causality
violation can be observed. We show how to formulate an observable whose
detection would signal causality violation. We study the range of energies
(relative to Λ) and couplings to which the observable can be used.Comment: Latex, 30 page