[3] Most of Steve Keen's recent work focuses on modeling Hyman Minsky's financial instability hypothesis and Irving Fisher's debt deflation.

[4][5] The hypothesis predicts that an overly large private debt to GDP ratio can cause deflation and depression.

Keen challenges the theory and pedagogy of "perfect competition" and "monopoly" as polar opposites from multiple angles, arguing that they are contradictory and incoherent taken as a whole.

[8] Keen's article on "profit maximisation, industry structure, and competition"[9] has had counter-arguments by Paul Anglin.

[11] Keen criticises the economics of climate change generally and the 2018 work by Nordhaus in particular: "economists made their own predictions of damages, using three spurious methods: assuming that about 90% of GDP will be unaffected by climate change, because it happens indoors; using the relationship between temperature and GDP today as a proxy for the impact of global warming over time; and using surveys that diluted extreme warnings from scientists with optimistic expectations from economists.

Keen also argues that regressions of the GSP of states in the US to average temperature are flawed as the states have similar per capita income, that other factors are more important to GSP rather than average temperature, and that assuming the weak correlation found would continue to hold true with further global warming is begging the question.

Correcting for these errors makes it feasible that the economic damages from climate change are at least an order of magnitude worse than forecast by economists, and may be so great as to threaten the survival of human civilization.

"[12][13] In August 2015, Keen endorsed Jeremy Corbyn's campaign in the Labour Party leadership election.

[14] Keen ran as a senate candidate for The New Liberals in New South Wales during the 2022 Australian federal election.

[15][16] Keen was in favour of the UK leaving the European Union, stating mainstream economists were over-certain and exaggerating the likely effects following the country's withdrawal.

[21] Matthijs Krul[22] maintains that Keen, while broadly accurate in his criticism of the neoclassical synthesis, generally misrepresents Marx's views in Debunking Economics and in earlier work when asserting that, in the production of commodities, machinery produces more value than it costs.

[23] Austrian School economists Robert P. Murphy and Gene Callahan claim Keen's 2001 book "suffers from many of the very faults of which he accuses the mainstream".

They praise his critique of perfect competition and his chapter on dynamic vs. static models, whilst they criticise his attempts at objective value theory and what they claim is his misrepresentation of the Austrian School interpretation of Say's law.