Soon after, Toulmin was hired by the Ministry of Aircraft Production as a junior scientific officer, first at the Malvern Radar Research and Development Station and later at the Supreme Headquarters of the Allied Expeditionary Force in Germany.

At the end of World War II, he returned to England to earn a Master of Arts degree in 1947 and a PhD in philosophy from Cambridge University, subsequently publishing his dissertation as An Examination of the Place of Reason in Ethics (1950).

While at Leeds, he published one of his most influential books in the field of rhetoric, The Uses of Argument (1958), which investigated the flaws of traditional logic.

In 1960, Toulmin returned to London to hold the position of director of the Unit for History of Ideas of the Nuffield Foundation.

While at the University of California, Santa Cruz, Toulmin published Human Understanding: The Collective Use and Evolution of Concepts (1972), which examines the causes and the processes of conceptual change.

[4] In 1973, while a professor in the Committee on Social Thought at the University of Chicago, he collaborated with Allan Janik, a philosophy professor at La Salle University, on the book Wittgenstein's Vienna, which advanced a thesis that underscores the significance of history to human reasoning: Contrary to philosophers who believe the absolute truth advocated in Plato's idealized formal logic, Toulmin argues that truth can be a relative quality, dependent on historical and cultural contexts (what other authors have termed "conceptual schemata").

From 1975 to 1978, he worked with the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research, established by the United States Congress.

[7] The NEH report of the speech further quoted Toulmin on the need to "make the technical and the humanistic strands in modern thought work together more effectively than they have in the past".

By contrast, Toulmin contends that many of these so-called standard principles are irrelevant to real situations encountered by human beings in daily life.

In Human Understanding (1972), Toulmin suggests that anthropologists have been tempted to side with relativists because they have noticed the influence of cultural variations on rational arguments.

In other words, the anthropologist or relativist overemphasizes the importance of the "field-dependent" aspect of arguments, and neglects or is unaware of the "field-invariant" elements.

In order to provide solutions to the problems of absolutism and relativism, Toulmin attempts throughout his work to develop standards that are neither absolutist nor relativist for assessing the worth of ideas.

In Cosmopolis (1990), he traces philosophers' "quest for certainty" back to René Descartes and Thomas Hobbes, and lauds John Dewey, Wittgenstein, Martin Heidegger, and Richard Rorty for abandoning that tradition.

Similarly, Toulmin sensed a thinning of morality in the field of sciences, which has diverted its attention from practical issues concerning ecology to the production of the atomic bomb.

Toulmin did not realize that this layout could be applicable to the field of rhetoric and communication until his works were introduced to rhetoricians by Wayne Brockriede and Douglas Ehninger.

By reviving casuistry (also known as case ethics), Toulmin sought to find the middle ground between the extremes of absolutism and relativism.

In this book, Toulmin attacks Thomas Kuhn's account of conceptual change in his seminal work The Structure of Scientific Revolutions (1962).

Toulmin criticized the relativist elements in Kuhn's thesis, arguing that mutually exclusive paradigms provide no ground for comparison, and that Kuhn made the relativists' error of overemphasizing the "field variant" while ignoring the "field invariant" or commonality shared by all argumentation or scientific paradigms.