An event (such as a choice or action) is determined when there are conditions obtaining earlier (such as the decrees of fate or the foreordaining acts of God or antecedent causes plus laws of nature) whose occurrence is a sufficient condition for the occurrence of the event. In other words, it must be the case that if these earlier determining conditions obtain, then the determined event will occur.
Kane points out that while determinism is "a kind of necessity," it is a "conditional necessity" in that a determined event is inevitable only if the proper conditions arise to determine it. For example, John did NOT have to go to Samarra no matter what the preceding conditions were. Had those conditions been different, he might have been determined by THEM to go to Damascus instead. But they were such that he was determined to go to Samarra.