In this chapter I argue that in order to secure some of his system's key commitments, Fichte employs argumentation essentially patterned after the technique of practical postulation in Kant.¹ This is a mode of reasoning that mobilizes a distinctly Kantian notion of nonepistemic justification, which itself is premised upon a broadly Kantian conception of the nature of reason. Succinctly stated, such argumentation proceeds essentially as follows: (1) by the basic nature and operations of rationality, every rational being is, as such, committed to e as an ultimate end (final purpose, highest goal); (2) e can be understood as actually attainable only if descriptive proposition p is assented to; (3) we cannot, in principle, possess genuine evidence for or against p; therefore, (4) while we do not have (and never could have) good epistemic grounds for assenting to p, we do have (and always will have) perfectly sufficient rational grounds for doing so. While this assent has no basis in pertinent evidence, it nonetheless has an unshakable foundation in the basic operations and requirements of rationality. This is so because this assent (a) sustains a commitment integral to rationality as such and (b) affirms a proposition that no evidence could ever discredit.