¹ See e.g. Robinson, P. H., Fundamentals of Criminal Law (2nd ed., Boston: Little, Brown, 1995), 250Google Scholar; LaFave, W. R., Criminal Law (3rd ed., St Paul, Minnesota: West, 2000), 195–202Google Scholar; Dressier, J., Understanding Criminal Law (3rd ed., New York: Lexis, 2001), 81–93Google Scholar; Williams, G., Criminal Law: The General Part (2nd ed., London: Stevens, 1961), 1–16Google Scholar; Wilson, W., Criminal Law (2nd ed., London: Longman, 2003), 72–6Google Scholar; Smith, J. C. & Hogan, B., Criminal Law (10th ed., by Smith, J. C., London: Butterworths, 2002), 30–68Google Scholar; Gordon, G. H., The Criminal Law of Scotland (3rd ed., by Christie, M. G. A., Edinburgh: Green, 2000), vol. I, 60–81Google Scholar. But contrast Ashworth, A. J., Principles of Criminal Law (4th ed., Oxford: Oxford University Press, 2003), 99–114Google Scholar; Simester, A. P. and Sullivan, G. R., Criminal Law: Theory and Doctrine (2nd ed., Oxford: Hart, 2003), 71–86Google Scholar: what is required is not an ‘act’, but ‘voluntariness’.

² The ‘voluntary’, as legal theorists typically use the term, thus excludes the involuntary: what is done under duress, whilst not done ‘voluntarily’ in ordinary usage, counts as a ‘voluntary’ act in this sense.

³ See Hill v Baxter [1958] 1 Q. B. 277Google Scholar.

⁴ Robinson v California 370 U. S. 660 (1962)Google Scholar.

⁵ Martin v State 17 So.2d 427 (1944)Google Scholar. Compare Winzar v Chief Constable of Kent (1983)Google Scholar The Times, 28 March (being found drunk in a highway); see Wilson, Criminal Law (n. 1 above), 73–4.

⁶ See e.g. Wilson, Criminal Law (n. 1 above), 77–94; Dressier, Understanding Criminal Law (n. 1 above), 101–5.

⁷ See Husak, D., ‘Does Criminal Liability Require an Act?’, Philosophy and the Criminal Law: Principle and Critique, Duff, R. A. (ed.) (Cambridge: Cambridge University Press, 1998), 60CrossRefGoogle Scholar, at 67–73.

⁸ Criminal Attempts Act 1981, s. 1(1); Model Penal Code s. 5.01(l)(c).

⁹ See Morris, H., ‘Punishment for Thoughts’, The Monist 49, No. 3 (July 1965), 1Google Scholar; Duff, R. A., Criminal Attempts (Oxford: Oxford University Press, 1996), 63–4Google Scholar.

¹⁰ See, respectively, Misuse of Drugs Act 1971, s. 5; Prevention of Crime Act 1953, s. 1; Forgery and Counterfeiting Act 1981, s. 16(2); Firearms Act 1968 s. 1(1).

¹¹ See, e.g., Explosive Substances Act 1883, s. 3 (possession of explosives with intent to endanger life or property); Firearms Act 1968, s. 16 (possession of firearms with intent to injure); Criminal Damage Act 1971 s. 3 (possession of something with intent to use it to damage property).

¹² This is an issue which has exercised English courts dealing with offences involving the unknowing ‘possession’ of drugs: Warner v Metropolitan Police Commissioner [1969] 2 A. C. 256Google Scholar; McNamara [1988] 87 Cr. App. Rep. 246Google Scholar; Smith & Hogan, Criminal Law (n. 1 above), 127–31.

¹³ See, e.g., Wilson, Criminal Law (n. 1 above), 75–6; Ashworth, Principles of Criminal Law (n. 1 above), 109–10; Simester & Sullivan, Criminal Law (n. 1 above), 85–6; Smith & Hogan, Criminal Law (n. 1 above), 59; LaFave, Criminal Law (n. 1 above), 211. But contrast the stipulation in Model Penal Code s. 2.01(4), on which see Robinson, Fundamentals of Criminal Law (n. 1 above), 261–2.

¹⁴ See Hill v Baxter (n. 3 above). I leave aside here the problems that this argument raises, if driving through a red light is a strict liability offence for which no mens rea is required (on which see Hart, H. L. A., ‘Acts of Will and Responsibility’, in his Punishment and Responsibility (Oxford: Oxford University Press, 1968), 90Google Scholar), most notably the problem that a similarly voluntary act is found in the case of the unforeseeable fit.

¹⁵ See Hornsby, J., ‘The Poverty of Action Theory’, Philosophical Inquiry 21 (Winter 1999), 1CrossRefGoogle Scholar, at 1.

¹⁶ Moore, M. S., Act and Crime (Oxford: Oxford University Press, 1993)Google Scholar; Placing Blame: A Theory of Criminal Law (Oxford: Oxford University Press, 1997)Google Scholar, especially chs. 1, 5, 6.

¹⁷ Placing Blame (n. 16 above), 35. Moore actually says there that the law ‘must punish all and only’ those who are thus culpable: but it turns out in ch. 18 that a proper concern for liberty will on balance preclude the criminalization of many kinds of morally wrongful action, including at least most of those that liberals would not want to criminalise.

¹⁸ Act and Crime (n. 16 above). The hyphenation makes the point that, for Moore, acts are to be identified neither with bodily movements, nor with volitions, but with the ‘complex event volitions-causing-movements’ (p. 113).

¹⁹ Act and Crime (n. 16 above), 4.

²⁰ See Act and Crime (n. 16 above), ch. 7. Moore does allow one type of exception to the act requirement: we can properly be held criminally liable for some omissions, when we breach a stringent positive duty to act; see Act and Crime, 54–9; Placing Blame (n. 16 above), 262–86.

²¹ See Act and Crime (n. 16 above), 20–2, 35–7; and text at nn. 10–14 above.

²² However, although I do not share Moore's metaphysical views, or his conception of law as a functional kind (see Placing Blame, n. 16 above, 20–22), there is more to be said for the claim that conduct should be brought within the reach of the criminal law in order to provide for its retributive punishment than many would allow: see Duff, R. A., ‘Crime, Prohibition and Punishment’, Journal of Applied Philosophy 19, No. 2 (Summer 2002), 97CrossRefGoogle Scholar.

²³ See e.g. Williams, G., Textbook of Criminal Law (2nd ed., London: Stevens, 1983), 147–8Google Scholar; Smith & Hogan, Criminal Law (n. 1 above), 37; LaFave, Criminal Law (n. 1 above), 208–10; Dressier, Understanding Criminal Law (n. 1 above), 83–6.

²⁴ Hornsby, J., ‘Action and Aberration’, University of Pennsylvania Law Review 142, No. 5 (May 1994), 1719Google Scholar; ‘The Poverty of Action Theory’ (n. 15 above); also her ‘On What's Intentionally Done’, Action and Value in Criminal Law, Shute, S., Gardner, J., Horder, J. (eds.) (Oxford: Oxford University Press, 1993), 55Google Scholar; and Williams, B., ‘The Actus Reus of Dr Caligari’, University of Pennsylvania Law Review 142, No. 5 (May 1994), 1661Google Scholar.

²⁵ ‘The Poverty of Action Theory’ (n. 15 above), 3, 6; and see p. 13—‘an action is an event of someone's doing something intentionally’. The qualification is that there are things we can do without moving our bodies— ‘just by thinking’ or ‘by staying still’ (‘The Poverty of Action Theory’, n. 6): I discuss such cases in s. 3 below.

²⁶ ‘The Poverty of Action Theory’ (n. 15 above), 15; see ‘On What's Intentionally Done’ (n. 24 above), 69–73.

²⁷ See text at nn. 18–20 above.

²⁸ Gross, H., A Theory of Criminal Justice (New York: Oxford University Press, 1979), 56Google Scholar; see Husak, D., Philosophy of Criminal Law (Totowa, N. J.: Rowman & Littlefield, 1987), 108Google Scholar; Moore, Act and Crime (n.16 above), 20–21.

²⁹ See Husak, ‘Does Criminal Liability Require an Act?’ (n. 7 above); also Simester, A. P., ‘On the So-called Requirement for Voluntary Action’, Buffalo Criminal Law Review 1, No. 2 (Spring 1998), 403Google Scholar; and Glazebrook, P. R., ‘Situational Liability’, in Reshaping the Criminal Law, Glazebrook, P. R. (ed.) (London: Stevens, 1978), 108Google Scholar.

³⁰ See text at nn. 4–5, 10–13 above; Husak, Philosophy of Criminal Law (n. 28 above), 100–102.

³¹ Compare Hornsby, ‘The Poverty of Action Theory’ (n. 15 above), 15, on the need for an account of action that ‘combines suitably with an account of all the moral psychological notions and... with an understanding of the social world’.

³² Moore, Act and Crime (n. 16 above), 134–5.

³³ Davidson, D., ‘Agency’, in his Essays on Actions and Events (Oxford: Oxford University Press, 1980), 43Google Scholar, at 43–4.

³⁴ See Danto, A. C., Analytical Philosophy of Action (Cambridge: Cambridge University Press, 1973), ixGoogle Scholar.

³⁵ See e.g. Danto, A. C., ‘Basic Actions’, The Philosophy of Action, White, A. (ed.) (Oxford: Oxford University Press, 1973), 43Google Scholar, as against Moore, Act and Crime (n. 16 above).

³⁶ See Hornsby, J., Actions (London: Routledge, 1980)Google Scholar, as against Duff, Criminal Attempts (n. 9 above), 278–92.

³⁷ Of course they amount to doings or commissions, they have an impact on the world, only in virtue of their social settings of conventions, understandings or expectations: but such settings are crucial to action as a social phenomenon.

³⁸ Though voting could, for instance, make me liable on a charge of conspiracy.

³⁹ See generally Smith & Hogan, Criminal Law (n. 1 above), 61–3.

⁴⁰ Theft Act 1968, s. 3(1): see Smith & Hogan, Criminal Law (n. 1 above), 513–27.

⁴¹ See Wilson, Criminal Law (n. 1 above), 415.

⁴² ‘Insulting behaviour’ is criminal under English law, but only if it is intended or likely to cause immediate unlawful violence or the expectation of such violence: Public Order Act 1986, s. 4.

⁴³ Moore argues that keeping still often essentially involves bodily movings (either muscle flexings to prevent the limbs from moving, or displacement movements of other parts of the body); and that if no such movings are involved, there is no action (Act and Crime, n. 16 above, 87–8, drawing on Vermazen, B., ‘Negative Acts’, Essays on Davidson, Actions and Events, Vermazen, B. & Hintikka, M. (eds.) (Oxford: Oxford University Press, 1985)Google Scholar; Placing Blame, n. 16 above, 271–3). But our understanding of the guardsman's standing still as something to explain in terms of his reasons (and also to admire) is not affected by whether it involved any such movement: my understanding and my judgement are not altered if I find out that, contrary to my initial belief, such movement was involved.

⁴⁴ See further Duff, Criminal Attempts (n. 9 above), ch. 11, drawing on (among others) Melden, A. I., Free Action (London: Routledge, 1961)Google Scholar; Gustafson, D., Intention and Agency (Dordrecht: Reidel, 1986)Google Scholar.

⁴⁵ To avert some misunderstandings, I should perhaps add that by ‘practical reasoning’ here I do not mean only those rich kinds of reasoning that connect individual actions to larger conceptions of the right or the good, or only those kinds of reasoning that are manifested in some occurrent process of deliberation; any action that is done for a reason actualises the results of practical reasoning.

⁴⁶ See Criminal Attempts (n. 9 above), chs. 9–11.

⁴⁷ Al Mele pressed this point on me in discussion.

⁴⁸ Hornsby, ‘Action and Aberration’ (n. 24 above), 1738–9.

⁴⁹ See Duff, R. A., Punishment, Communication, and Community (New York: Oxford University Press, 2001), 56–66Google Scholar. The distinction between ‘mala in se’ and ‘mala prohibita’ is neither clear cut nor uncontroversial, but that problem need not concern us here.

⁵⁰ It should be obvious that I am drawing here on the Davidsonian idea that we can ascribe Ψ-ing to me as an action if I Ψ in or by intentionally Φ-ing (Davidson, ‘Agency’ (n. 33 above), 45–6), although in the service of a conception of action quite different from his. Note that, although I am now explicating the act requirement in terms of a conception of action that essentially involves intention, the satisfaction of the act requirement can still be separated, as theorists orthodoxly separate it, from the satisfaction of whatever mens rea requirements are specified for the offence: I Φ intentionally, but can unintentionally Ψ in or by Φ-ing.

⁵¹ See text following n. 29 above.

⁵² On which see Feinberg, J., Harmless Wrongdoing (New York: Oxford University Press, 1988), especially 1–38Google Scholar, 318–38; see Duff, R. A., ‘Harms and Wrongs’, Buffalo Criminal Law Review 5, No. 1 (Fall 2001), 13Google Scholar.

⁵³ See text at nn. 8–9 above. Husak even casts doubt on whether an act should be required as a condition of liability for such firm criminal intentions, if sufficiently overwhelming evidence could be found without the kind of act that current attempt statutes require: see Husak, ‘Does Criminal Liability Require an Act?’ (n. 7 above), 89–90.

⁵⁴ See Duff, Criminal Attempts (n. 9 above), 385–95.

⁵⁵ See Duff, Criminal Attempts (n. 9 above), 35–7.

⁵⁶ This is Moore's approach, in distinguishing ‘the act requirement’ from ‘the actus reus requirement’; see Act and Crime (n. 16 above).

⁵⁷ See text at n. 14 above; also Moore, Act and Crime (n. 16 above), 35–7.

⁵⁸ See also Simester, ‘On the So-Called Requirement for Voluntary Action’ (n. 29 above), 407–8.

⁵⁹ Act and Crime (n. 16 above), 21.

⁶⁰ Moore seems to assume that an act (or omission) is required as the object of liability: that is what ‘is being punished’. But one might as plausibly require a suitable act or omission simply as a condition of liability for a condition or state of affairs.

⁶¹ There would then be further questions about what should count as acquiring a condition, when the agent did not intend to acquire it. Should we attribute Mr Martin's condition, of being drunk in public, to his prior action of getting drunk in his home; or should we treat the police intervention as ‘the cause’ (see text at n. 5 above; Moore, Act and Crime (n. 16 above), 36–7)? Should we take a different view if he was drunk in public because he had got drunk in someone else's house and been forcibly ejected (see Wilson, Criminal Law (n. 1 above) 73–4)?

⁶² See Glazebrook, ‘Situational Liability’ (n. 29 above) for a useful collection of examples. For an incisively critical discussion of possession offences, see Dubber, M. D., ‘Policing Possession: The War on Crime and the End of Criminal Law’, Journal of Criminal Law and Criminology 91 (Summer 2001), 829CrossRefGoogle Scholar.

⁶³ See n. 10 above, and accompanying text. Sometimes, of course, what is possessed can be dangerous in and of itself, without further human action: unstable explosives, or various kinds of poisonous substance that might leak, for instance. These kinds of case usually involve corporations rather than private individuals, and are dealt with under health and safety or environment laws; they could also, in principle, fall under endangerment laws in jurisdictions that have general offences of endangerment— see Model Penal Code s. 211.2; Gordon, The Criminal Law of Scotland (n. 1 above), vol. II, 427–30.

⁶⁴ See n. 11 above, and accompanying text.

⁶⁵ See n. 10 above. There are other strategies that fall between these two extremes; see, e.g., Explosive Substances Act 1993, s. 4 (possession of explosives that the defendant cannot show he had for a lawful purpose).

⁶⁶ See Ashworth, Principles of Criminal Law (n. 1 above), 51–2; and more generally von Hirsch, A., ‘Extending the Harm Principle: "Remote" Harms and Fair Imputation’, in Harm and Culpability, Simester, A. P. and Smith, A. T. H. (eds.) (Oxford: Oxford University Press, 1996), 259CrossRefGoogle Scholar.

⁶⁷ One could portray the question here as that of whether failure to divest myself of the gun constitutes ‘possession’ of it: but an answer to that question (which cannot be reached by a simple examination of the ordinary meaning of ‘possession’) would reflect, rather than grounding, the decision about criminalization.

⁶⁸ See Katz, L., Bad Acts and Guilty Minds (Chicago: Chicago University Press, 1987), 143CrossRefGoogle Scholar.

⁶⁹ See at n. 6 above.

⁷⁰ See Smith & Hogan, Criminal Law (n. 1 above), 60; for some other clear examples, see e.g. the duties imposed on bankrupts by ss. 353–5 and 361 of the Insolvency Act 1986.

⁷¹ See Gibbins and Proctor [1918] 13 Cr. App. Rep. 134Google Scholar.

⁷² See Feinberg, J., Harm to Others (New York: Oxford University Press, 1984), ch. 4Google Scholar; also Robinson, Fundamentals of Criminal Law (n. 1 above), 424–5.

⁷³ The same distinction holds if the duty to act is special rather than general. A parent who fails to feed his child is guilty of neglecting the child (an offence of pure omission) even if the child is not harmed (because someone else intervenes), and whatever his intent: see Children and Young Person's Act 1033, s. l(2)(a).

⁷⁴ Pace Feinberg, Harm to Others (n. 72 above), ch. 4.

⁷⁵ I leave the question of liability for inchoate offences of attempt or endangerment aside here; we must answer the question about complete offences first.

⁷⁶ Though the very idea of an omission, or of a failure to act, presupposes some expectation that the person would act—an expectation that is often a normative matter of the person's duties or responsibilities (see Casey, J., ‘Actions and Consequences’, Morality and Moral Reasoning, Casey, J. (ed.) (London: Methuen, 1971), 155)Google Scholar. The question then is: which of these expectations should the criminal law enforce?

⁷⁷ See at n. 68 above.

⁷⁸ If he is not a responsible agent, the ascription of agency becomes more complicated: for whilst we can ascribe agency without ascribing full criminal or moral responsibility, the ascription itself is liable to be qualified.

⁷⁹ See text at n. 37 above.

⁸⁰ See, e.g., Bayles, M. D., ‘Character, Purpose, and Criminal Responsibility’, Law and Philosophy 1 (1982), 5Google Scholar; Finklestein, C., ‘Duress: A Philosophical Account of the Defense in Law’, Arizona Law Review 37 (1995), 251Google Scholar; Huigens, K., ‘Virtue and Inculpation’, Harvard Law Review 108 (1995), 1423Google Scholar. For critical discussion, see Duff, R. A., ‘Virtue, Vice, and Criminal Liability’, Buffalo Criminal Law Review 6 (Spring 2003), 101Google Scholar.

⁸¹ This paper was written during my tenure of a Leverhulme Major Research Fellowship; I am very grateful to the Leverhulme Trust for this support. I am also grateful to Jennifer Hornsby, and to participants in the Royal Institute of Philosophy Conference on Action and Agency at which an earlier version of this paper was given, for helpful comments and suggestions.