Synthesized answer
The provided passages introduce Immanuel Kant's *Critique of Practical Reason* and discuss its translation and introduction. The introduction, by Stephen Engstrom, is noted to discuss the work's place within Kant's critical philosophy, its relationship to Kant's ethics, and its practical purpose, as well as offering an outline of Kant's argument [Passage 1].
However, the passages do not provide explanations of the key concepts within *Critique of Practical Reason* in my own words, nor do they offer definitions or elaborations on these concepts. Therefore, I cannot answer the question about explaining the key concepts using the provided text.
Synthesized from the book passages below. Chat with the book on Feynman for follow-up.
From the book
Title: Critique of Practical Reason by Immanuel Kant Description: With this volume, Werner Pluhar completes his work on Kant's three Critiques, an accomplishment unique among English language translators of Kant. At once accurate, fluent, and accessible, Pluhar's rendition of the Critique of Practical Reason meets the standards set in his widely respected translations of the Critique of Judgment (1987) and the Critique of Pure Reason (1996). Stephen Engstrom's Introduction discusses the place of the second Critique in Kant's critical philosophy, its relation to Kant's ethics, and its…