In this paper I explore the concept of tolerance and suggest a description of that concept that could be accepted regardless of the political theory one supports. Since a neutral perception of the limits of tolerance is impossible, this paper offers a guideline for a substantive-liberal or a perfectionist-liberal approach to it. The limits of tolerance are described through the principles of reciprocity and proportionality. The former explains why intolerance should not be tolerated whereas the latter prescribes how and to (...) what extent it should be tolerated. The cumulative effect of these principles is that apart from extremely rare occasions intolerance should not be tolerated at any time. (shrink)