Failure to agree is not a failure

Based on the patterns of phi-agreement with post-verbal subjects in Hebrew, I argue against the idea that failure to establish a phi-agreement relation between a phi-probe and its putative target (e.g., due to intervention) results in ungrammaticality, or a “crash”; at the same time, I demonstrate that phi-agreement also cannot be optional. At first glance, these two claims—that phi-agreement is neither optional, nor does its failure result in ungrammaticality—might seem contradictory. However, I argue that there is a third possibility, which is in fact the only one that can account for the data under consideration: phi-agreement must be attempted by every phi-probe; but if it fails (e.g., due to the presence of an intervener), its failure is systematically tolerated. tolerated.