Haack is a graduate of the University of Oxford and the University of Cambridge. At Oxford, she studied at St. Hilda's College, where her first philosophy teacher was Jean Austin, the widow of J. L. Austin. She also studied Plato with Gilbert Ryle and logic with Michael Dummett. David Pears supervised her B.Phil. dissertation on ambiguity. At Cambridge, she wrote her Ph.D. under the supervision of Timothy Smiley. She held the positions of Fellow of New Hall, Cambridge and professor of philosophy at the University of Warwick before taking her current position at the University of Miami.

Haack's major contribution to philosophy is her epistemological theory called foundherentism, which is her attempt to avoid the logical problems of both pure foundationalism (which is susceptible to infinite regress) and pure coherentism (which is susceptible to circularity). She illustrates this idea with the metaphor of the crossword puzzle. A highly simplified version of this proceeds as follows: Finding an answer using a clue is analogous to a foundational source (grounded in empirical evidence). Making sure that the interlocking words are mutually sensible is analogous to justification through coherence. Both are necessary components in the justification of knowledge.

She wrote a play, We Pragmatists ...: Peirce and Rorty in Conversation, consisting entirely of quotes from both philosophers. She performed the role of Peirce. Haack published a vigorous essay in the New Criterion, taking strong exception to many of Rorty's views, especially his claim to be a sort of pragmatist.

Haack (1998) is highly critical of the view that there is a feminine perspective on reasoning, logic, scientific method, and scientific truth, stating that many feminist critiques of science and philosophy as being concerned that the outcomes of scientific inquiry be "politically correct".

She has written for Free Inquiry magazine and the "Council for Secular Humanism". Haack's work has been reviewed and cited in the popular press, such as The Times Literary Supplement as well as in academic journals.

Haack is an honorary member of Phi Beta Kappa Society and Phi Kappa Phi, a past President of the Charles S. Peirce Society, and a past member of the U.S./UK Educational Commission.