Critique of Practical Reason by Immanuel Kant (1788)

After completing Groundwork of the Metaphysics of Morals, you will notice Kant sees reason as an important part of navigating morality. Critique of Practical Reason offers a broader look at reason and applies it to situations besides morality. Readers may be interested in Critique since it will take familiar concepts and apply them within Kant’s wider philosophical system.  

Critique of Pure Reason by Immanuel Kant (First published in 1781, republished in 1787)

Critique of Pure Reason was published before Groundwork but offers another look at certain concepts referenced in the book. He hopes to encourage the development of metaphysics as a legitimate discipline by defining its purpose and limits. Kant believes metaphysics can only grow through synthetic a priori propositions and hopes to prove these are possible. As we have now seen in Groundwork, Kant wants to establish a synthetic a priori understanding of morality.

• Critique of Pure Reason on SuperSummary  

Prolegomena to Any Future Metaphysics by Immanuel Kant (1783)

Prolegomena to Any Future Metaphysics will be useful to any reader leaving Groundwork curious about the mechanics of metaphysics. Prolegomena attempts to understand if metaphysics can operate by scientific rules. Since science is based on concrete observation and metaphysics is based on a priori knowledge, Kant wants to see if it is possible to reconcile these seemingly oppositional fields.