By means of careful analysis of relevant writings by Hobbes, Rousseau, Kant, Hegel, and Marx, the author argues that the concept of practical necessity is key to understanding the nature and the extent of human freedom. Practical necessity here means being, or believing oneself to be, constrained to act in certain ways in the absence (whether real or imagined) of other, more attractive options, or by the high costs attached to pursuing other options. Agents become subject to practical necessity because of economic, social, and historical forces over which they have, or appear to have, no effective control, while the extent to which they are subject to this form of necessity varies according to the amount of economic and social power that one agent possesses relative to other agents. The concept of practical necessity is also shown to acknowledge how the beliefs and attitudes of social agents are, in large part, determined by social and historical processes in which they are caught up, and how the type of motivation that we attribute to such agents should recognize this fact. Another key theme is how Rousseau, Kant, Hegel, and Marx, in contrast to Hobbes, explain the emergence of the conditions of a free society in terms of a historical process that is initially governed by practical necessity. The role that this form of necessity plays in explaining historical necessity invites thefollowing question: to what extent arehistorical agents genuinely subject to practical and historical necessity?