 MacCallum’s framework is particularly well suited to the clarification of such issues. For this reason, theorists working on the measurement of freedom tend not to refer a great deal to the distinction between positive and negative freedom. This said, most of them are concerned with freedom understood as the availability of options. And the notion of freedom as the availability of options is unequivocally negative in Berlin’s sense at least where two conditions are met: first, the source of unfreedom is limited to the actions of other agents, so that natural or self-inflicted obstacles are not seen as decreasing an agent’s freedom; second, the actions one is free or unfree to perform are weighted in some value-neutral way, so that one is not seen as freer simply because the options available to one are more valuable or conducive to one’s self-realization. Of the above-mentioned authors, only Steiner embraces both conditions explicitly. Sen rejects both of them, despite not endorsing anything like positive freedom in Berlin’s sense.