He was born at Fürstenwalde. He studied theology and philosophy under Friedrich Adolf Trendelenburg at Berlin, and eventually became a professor of philosophy at the University of Strasbourg (1872). In his Kants Analogien der Erfahrung ("Kant's Analogies of Experiences", 1876) he keenly criticized Immanuel Kant's transcendentalism, and in his chief work Idealismus und Positivismus ("Idealism and Positivism", 1879–1884, 3 volumes), he drew a clear contrast between Platonism, from which he derived transcendentalism, and positivism, of which he considered Protagoras the founder. Laas in reality was a disciple of David Hume. Throughout his philosophy he endeavours to connect metaphysics with ethics and the theory of education.
His chief educational works were Der deutsche Aufsatz in den ersten Gymnasialklassen (1868), and Der deutsche Unterricht auf höhern Lehranstalten (1872; 2nd ed. 1886). He contributed largely to the Vierteljahrsschrift für wissenschaftliche Philosophie (1880–82); the Literarischer Nachlass, a posthumous collection, was published at Vienna (1887).