Lange was born in Wald, near Solingen, the son of the theologian, Johann Peter Lange. He was educated at Duisburg, Zürich and Bonn, where he distinguished himself in gymnastics as much as academically. In 1852 he became a schoolmaster at Cologne; in 1853 Privatdozent in philosophy at Bonn; and in 1858 schoolmaster at Duisburg, resigning when the government forbade schoolmasters to take part in political activities.

Lange entered journalism as editor of the Rhein - und Ruhr - Zeitung in 1862 in the cause of political and social reform. His ceterum censeo can be considered to be the repeated demand for Bismarck's resignation. He was prominent in public affairs, yet found enough time to write most of his best known books, Die Leibesübungen (1863), Die Arbeiterfrage (1865, 5th ed. 1894), Geschichte des Materialismus (1866), and John Stuart Mills Ansichten über die soziale Frage (1866). He also wrote a number of works on pedagogy and psychology. In 1863, Lange supported the socialist leader Ferdinand Lassalle in an important trial concerning the constitutional guarantee of academic freedom. From 1864 to 1866, Lange was a member of the executive committee of the Association of German Labour Unions (Verband Deutscher Arbeitervereine), an early organisation of the German labour movement. One of his colleagues there was August Bebel, the Social - Democratic leader.

In 1866, discouraged by affairs in Germany, he moved to Winterthur, near Zürich, to become connected with the democratic newspaper, Winterthurer Landbote. In 1869 he was Privatdozent at Zürich, and the next year he was appointed professor of inductive philosophy, a new position. He was also engaged in the Swiss Democratic movement and helped write the constitution of the Canton of Zurich. This was distinguished by the use of “direct democratic” measures such as referendum and recall. Still in Zürich he recognized first signs of his illness, which led several year later to his death. The strong French sympathies of the Swiss in the Franco - Prussian War as well as the prospect for a pension for his wife in the case of his death led to his speedy resignation. He had an offer from the universities of Würzburg, Königsberg, Kiel, Gießen and Jena, but in 1872 he accepted a professorship at the University of Marburg. He is sometimes credited with founding the Marburg School of Neo - Kantianism, along with his star pupil, Hermann Cohen. It was Cohen, however, who pioneered the Marburg School's characteristic logicist interpretation of Kantian philosophy. In later years, Lange accepted Cohen's refutation of a psychological interpretation of the a priori, to which he himself had once subscribed.

Although he rejected Marxist materialism, Lange continued to influence the German Social - Democratic movement. He favoured an ethically motivated, reformist socialism. He especially influenced some leaders of the Lassallean General German Workers' Union and, posthumously, the Revisionist theoretician Eduard Bernstein, whose slogan "Kant, not cant" proclaimed his abandonment of Marxian 'scientific socialism' in favour of a Neo - Kantian, ethically based social reformism. Subsequent leaders of the Marburg School, such as Cohen and Natorp, continued this association with the reformist wing of the SPD. Unhappily, his body was already stricken with disease. He no longer played a role in the unification of the Lassalleans with Bebel's socialists into the unified SPD in May 1975. After a lingering illness, probably gastro - intestinal cancer, he died in Marburg in November of that year. His Logische Studien (Logical Studies) were published by Hermann Cohen in 1877. Lange also wrote a number of literary studies which were published posthumously. His main work, the Geschichte des Materialismus is a didactic exposition of principles rather than a history in the proper sense. According to Lange, to think clearly about materialism is to refute it.

There is a comprehensive school named after him, the Friedrich - Albert - Lange - Gesamtschule, in Wald, his birthplace, which is now part of the city of Solingen.