Christian August Crusius was born in 1715 in Leipzig, where he was educated first at a grammar school and then at the university; there he became a follower of Adolf Friedrich Hoffmann, a Pietist highly critical of Wolff. Shortly after graduation Crusius accepted the extraordinary professorship of philosophy in 1744 and then the more prestigious (and remunerative) ordinary professorship in theology in 1750. Until his death, in 1775, he then devoted his intellectual energies to a wide variety of primarily orthodox theological issues (often in opposition to those of his more reform-minded colleague, Johann August Ernesti).

Crusius's publications in philosophy span a mere seven years, from 1743 to 1749. His dissertation, in 1743, Dissertatio de usu et limitibus principii rationis determinantis vulgo sufficientis (Dissertation on the Use and Limits of the Principle of Determining Reason, Commonly Called Sufficient Reason), contains a criticism of Wolff's principle of sufficient reason. His Entwurf der Notwendigen Vernunft-Wahrheiten (Sketch of the Necessary Truths of Reason, 1745) presents his distinctive metaphysical view, while his Weg zur Gewiβheit und Zuverläβigkeit der menschlichen Erkenntnis (Path to the Certainty and Reliability of Human Cognition, 1747) lays out his position on logical and epistemological issues. His Anweisung, vernünftig zu leben (Directions for Living Rationally, 1744) and Anleitung über natürliche Begebenheiten ordentlich und vorsichtig nachzudenken (Introduction to Proper and Cautious Reflections on Natural Events, 1749) treat ethics and natural philosophy respectively, so that he had covered a fairly comprehensive gamut of traditional philosophical topics by the time he turned to theology.