The Dualism of Practical Reason: The Profoundest Problem of ethics

Cinara Nahra


The aim of this article is to discuss and revisit what Sidgwick called the profoundest problem of ethics: the dualism of practical reason. I argue that Crisp’s dual source view provides a good solution for the dualism via the small cost principle showing that we have to balance agent relative and agent neutral reason in a kind of a rational “negotiation” between our egoistic and our altruistic motivations. I suggest, however, that in order to justify his solution it is necessary to go beyond Sidgwick establishing a limit for the acceptance of egoism as a legitimate method of ethics. I propose also that the dualism is not only the profoundest problem of ethics, but also one of the more serious, it is the biggest contemporary ethical puzzle of humankind, and whose practical solution is of paramount importance for the future of life on earth.




Dualism of practical reason; Dual source view ; Altruism; Egoism

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Bostrom, Nick 2002 “Existential Risks: Analysing Human Extinction Scenarios and Related Hazards” Journal of Evolution and Technology v.9 (2002)

Crisp, Roger (1996) “The Dualism of Practical Reason” p.53, Proceedings of the Aristotelian Society, vol. 96

Crisp, Roger Reasons and the Good 2006 (Oxford: Oxford University Press,2006)

Crisp, Roger 2015 The Cosmos of Duty: Henry Sidgwick’s Methods of Ethics (Oxford: Oxford University Press, 2015)

Hobbes, Thomas Leviathan [1651] 1996 (Oxford: Oxford University Press, 1996)

Hobbes, Thomas De Cive, The latin version [1647] 1983 (Oxford: Clarendon Press, 1983) ed.H. Warrender

Kant, I Critique of Practical Reason [1788] 2002 (Indianapolis/Cambridge: Hackett Publishing Company, 2002)

Kant, Immanuel Groundwork for the Metaphysics of Morals [1785] 2002 (New Haven and London: Yale University Press, 2002)

Lazari-Radek, Katarzyna de and Singer, Peter 2014 The Point of View of the Universe: Sidgwick and Contemporary Ethics (Oxford: Oxford University Press, 2014)

Phillips, David 2011 Sidgwickian Ethics (Oxford: Oxford University Press,2011)

Schultz, B 2004 Eye of the Universe: An Intellectual Biography (Cambridge: Cambridge University Press,2004)

Sidgwick, Henry 1874 The Methods of Ethics (London: Mac Millan and Co,1874) 1st ed.

Sidgwick, Henry The Methods of Ethics [1907] (1981) (USA: Hackett Publishing Company, 1981)7 th ed

Skorupski, John 2001 “Three Methods and a Dualism” Proceedings of the British Academy v. 109 (2001)

Bulletin of the atomic scientists available at

United Nation 2030 UN Agenda for Sustainable Development (available at

IPCC (Intergovernmental Panel on Climate Change) 2018 rapport available at file:///H:/My%20documents%202019%20HP%20computer/environment%20ipcc%20rapport.pdf





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