Schmid was born in 1761 in Heilsberg (Saxe-Weimar) into a family of church and state servants. After receiving an extensive intellectual education at home, Schmid studied theology at the University of Jena from 1778 to 1780, also attending lectures on philosophy and a wide range of other subjects. In 1780 Schmid took his theological exam at the Consistory in Weimar; one of his examiners was Johann Gottfried Herder who urged Schmid to pursue an academic career. In 1781, Schmid was hired by Baron von Hardenberg as private tutor to his son Friedrich (Novalis) during travels in the region of Brunswick. In 1782–84 Schmid had another appointment as private tutor, but left this position to return to the university in Jena. In summer 1785 he began to lecture on Kant’s critical philosophy, which he had begun to study in 1782. In 1787, Schmid was appointed vicar in his father’s parish in Wenigenjena; there Schmid on 22 February 1790 performed the wedding ceremony for Friedrich Schiller, with whom he had become friends in 1789, and Charlotte von Lengefeld.

In autumn 1791 Schmid left Jena to assume the chair of logic and metaphysics at the University of Gießen. In 1792, Schmid anonymously published two notorious sceptical treatises, Johann Joachim Müller’s Tractatus de tribus impostoribus and Theodor Ludwig Lau’s Meditationes philosophicae de Deo, mundo, homine. Having been found out by the authorities, Schmid in April 1793 was forbidden to preach and teach publicly and was suspended without pay for three months (cf. Haug 1995 for a detailed account of the scandal).

In the spring of 1793, Schmid left Gießen to return to Jena where he was appointed diaconus and in autumn he became professor of philosophy. In 1793–96 Schmid was involved in a fierce philosophical quarrel with fellow Jena professor and rising star Johann Gottlieb Fichte which culminated in Fichte publishing an “act of annihilation”. Originating in the controversy over Schmid’s concept of freedom, his so-called “intelligible fatalism”, the conflict concerned the very foundations of philosophy. Fichte and Schmid were also on opposing sides in the disputes among early Kantians about the foundation of natural law, its relation to morality and the justification of coercion (cf. van Zantwijk 2003; Kersting 1984, 50–69). As a result of his quarrel with Fichte, Schmid faced dwindling numbers of students and colleagues distancing themselves from him. This changed after Fichte had to leave Jena in 1799 following the atheism dispute (on the Schmid-Fichte controversy, see Graf 1995, 361–373; Frank 1997, 532–568). In 1798 Schmid was appointed professor of theology at Jena; in 1800 he was elected rector of the university, holding the office until mid-1801, and again in 1809.

With his teaching and publications – especially Kritik der reinen Vernunft im Grundrisse, Wörterbuch zum leichtern Gebrauch der Kantischen Schriften and Versuch einer Moralphilosophie – Schmid played an eminent role in the propagation of Kantianism in German academia in the 1780s and 1790s and was influential in the debates that led to the emergence of German Idealism. Schmid also published on empirical sciences and questions of methodology and in particular contributed to the establishment of psychology as an empirical discipline.

Schmid presents his system of natural law in Grundriß des Naturrechts, a concise textbook published in 1795, but also in his main work on moral philosophy, Versuch einer Moralphilosophie, which first appeared in 1790 to critical acclaim as it presented the first full-fledged system of moral philosophy based on Kantian principles. Questions of legal philosophy are discussed extensively in the elaboration of duties of justice towards others (1790, §§ 533–596). Schmid also touches on these topics in a shorter textbook on morals, Grundriß der Moralphilosophie (1793; 1800).

In Grundriß des Naturrechts the primary division of natural law is that between “pure” and “applied” natural law. “Pure natural law” comprises an analytical and a synthetic part. The first provides an analysis of the general concept of right (“Recht”) on the one hand – which proceeds according to a (slightly modified) Kantian table of categories with the headings of quantity, quality, reality, and modality – and of related concept, such as imputation, punishment etc. The synthetic part of pure natural law provides a real definition of right by developing the fundamental synthetic principle of natural law. “Applied natural law” then applies the idea and principle of right to nature and the conditions of human beings. In his division of applied natural law Schmid follows the traditional distinction between “absolute” (§§ 177–224) and “hypothetical” natural law (§§ 225–281), the first of which expounds the original, or innate, rights of human beings, while the latter is concerned with the possible ways of acquiring rights. Hypothetical natural law, in turn, has a general (§§ 226–256) and a particular part (§§ 257–281). The general part deals with the original appropriation of property (§§ 228–235) and the transfer of rights via contracts (§§ 238–256). Particular hypothetical natural law comprises the law of societies, particularly marriage (§§ 261–263), church (§§ 264–270), and the state (§§ 271–281).

Schmid derives the concept of right “Recht” and the principles of natural law from the moral law. The basis of natural law cannot be found in ‘material’ principles, such as eudaimonism or perfectionism, since these do not hold categorically and universally for all rational beings. Only a formal practical principle can ground natural law: the practical law of pure reason, which is the moral law. The moral law requires us to act according to rules that can hold as universal law for every free rational being. It hence forbids any use of freedom that, if universalized, would destroy itself. Natural law applies this principle to the external use of freedom in relation to others and connects it with the idea of coercion. Coercion is justified insofar as it counteracts actions that conflict with the freedom of others. An agent is permitted to resist (coerce) others whenever they hinder her in the morally, and thus juridically, permitted use of her freedom. Every rational being has three universal original rights, “allgemeine Urrechte”: personal freedom, the right to possess things, and personal equality, on which all other rights, be it innate human rights or more particular acquired rights, are based. The purpose of the state is to secure these rights by force. The state originates in the civil contract, which is in part a pact of union and in part a pact of subjection.