The discussion of Parfit's distinction between "subjective" and "objective" theories of reason by Smith in Ratio is of the version entitled Climbing the Mountain which is available for consultation here. As Smith mentions, however, in the course of the article replying to Parfit, the manuscript subsequently underwent some further significant changes producing the form reached at the end of 2008 which is available here. Climbing the Mountain does not formulate a distinction between "objective" and "subjective" theories of reasons but between desire-based and value-based theories of reason though Smith treats this as a distinction without a difference, assuming that desire-based theories are effectively the same as what Parfit later terms "subjective" theories and mutatis mutandis with "objective" theories and value-based ones.
In Climbing the Mountain Parfit introduces the distinction in broader terms than appear in the final published form of On What Matters. In the earlier form Parfit's distinction is first made in the second section of Chapter 1. The desire-based theory is initially presented as concerned with stating that our reasons for acting are grounded on actual present aims and desires though Parfit quickly complicates this by building in references to potential desires in hypothetical situations. The desire-based theory is understood to be a form of "internalism" about reasons, something that Parfit is less explicit about in the final published manuscript though the "subjective" theory discussed there clearly is also internalist.
The "value-based" theory, by contrast to the "desire-based" one, understands reasons for action as provided by the facts that make certain outcomes worth producing or preventing and is hence externalist. Not only do these theories describe reasons for action in different ways but they are often each thought to rule out the types of reason the other theory takes itself to have described. So, if, as Parfit is, one is an externalist about reasons for action, then, frequently (and certainly in Parfit's own case) one will deny that the other types of reason even exist.
The "internalist" theory as Parfit presents it is one that is broadly articulated in contemporary philosophy as dependent upon a "Humean" notion of motivation and I described it this way in a posting back in December. Notably, Smith defended an articulated version of the "Humean" theory sometime ago (in an article in Mind in 1987) so Smith and Parfit are at odds on some fundamental questions. However, the key point here is less with the "Humean" theory of motivation itself than with whether Parfit's distinctions have the force he thinks they do.
In the 2008 version of On What Matters Parfit has reached the formulation of the distinction that remains into the published work, the one between "subjective" and "objective" theories of reasons. The point of the distinction's difference from that used in Climbing the Mountain is to bring out the intentional quality of the claims involved in what the earlier manuscript had simply termed "value-based" views. As is clear from having looked at the chapter on "objective" theories of reasons, Parfit's understanding of these arises from the sense that "reasons are given by facts about the objects" of aims and desires. This reference to the "object" was missing in the formulation of "value-based" theories that Parfit used in Climbing the Mountain. Further, having identified this reference to "objects" in reasons Parfit can add that if we take the view that all reasons for action involve such "objects" then we are "objectivists" about reasons (or take reasons for action all to be intentional in nature). Smith is right in taking this to be equivalent to a "value-based" view as Parfit explicitly says it is but this does not mean that the account has not been filled out by making its intentional nature more apparent.
Now, the subjectivist theories of reasons will not simply deny that there are such "objects" present in reasons for actions. They will present reasons for actions as having a different structure than the objectivist has stated. Rather than taking the "facts" that provide reasons to have this object-oriented or intentional character the subjectivist rather views them as having reference to desires or aims and a subjectivist about reasons takes all reasons for action to be of this sort. Smith, however, cites also a passage from a version of Parfit's work dating from April 2008 (which is not available in the public domain) in which Parfit suggested that there could exist a theory that, whilst closer to objectivism than subjectivism was nonetheless distinct from both. According to the citation Smith provides from this version Parfit referred to "some Kantians" who held that "if we set ourselves any end or aim, we are not fully procedurally rational unless we also value the capacity of all other rational beings to set their ends and we commit ourselves to treating others only in ways to which they could rationally consent". In the passage cited by Smith, Parfit claims that such a Kantian view is "subjectivist" in appealing to what we would want or choose if fully informed. However, his general view is that it would be more appropriate to term holders of this view "systematic Coherentists" who take reasons to require commitment to such systematic coherence in order to be binding. The point Smith makes against Parfit in citing this passage is that such a Kantian view does provide us with "objective" reasons but not through its appeal to the place of "objects" in reasons but rather from the derivative character of such placing on the procedure of universalisation. That Parfit, at least at one point, entertained such a notion and then did not pay sustained attention to it, weakens his subsequent formulations that include Christine Korsgaard and Rawls amongst subjectivists about reasons.
Parfit's general account of "subjectivism", in any case, builds in a sense of reflection required for consideration of relevant facts at every point of declension after the simplest desire-based theory has been described. Since there is this reference to reflection it follows that "subjectivists" about reasons for action do not rest their case only upon reference to states (and thus they do not adopt a state-given reason or at least if one is involved it is combined with a reflective appeal as well). This is clear in the "subjectivist" theories Parfit lists such as the "error-free desire theory", "the telic desire theory", "the informed desire theory" and "the deliberative theory". When formulating the last of these Parfit reaches for another way of distinguishing between "objective" and "subjective" theories of reasons.
The "deliberative theory" is stated by Parfit to involve the claim that we have most reason to do whatever, after fully informed and rational deliberation, we would choose to do. And, put like this, the theory can appear to be an "objectivist" one when it is not. The difference between the "deliberative theory" and an "objectivist" theory is said by Parfit to consist in the kinds of rationality invoked in the two theories. The upholders of the "deliberative theory" appeal only to "procedural rationality" whilst the objectivist, by contrast, makes reference to "substantial" rationality. The difference is instructively stated. The "subjectivist" deliberative view is said to require involving reference to procedural rules and imagining "the important effects of our different possible acts" whilst the objectivist, by contrast, claims that there are telic desires and aims that "we all have strong and often decisive object-given reasons to have".
The difference between the two theories, for Parfit, concerns the way in which the reasons we give for holding something to constitute a reason for action are differently justified for the two sorts of theorists. Essentially, the "deliberative" theory holds that, given procedural constraints, if we would choose something after the process of reasoning, then we have decisive reasons given to act in the way indicated. By contrast, for the objectivist, it is rather the case that there exist decisive reasons to act in a certain way and given these reasons, substantive reasoning would confirm the rightness of acting in the way indicated.
However, after having set the distinction out in this way, Parfit concludes the distinction between the two views in a way that appears very unsatisfactory. Parfit writes:
These Objectivists appeal to normative claims about what, after ideal deliberation, we have reasons to choose, and ought rationally to choose. These Subjectivists appeal to psychological claims about what, after such deliberation, we would in fact choose.
This claim, from p. 63 of the published version of the work, appears wrong. It amounts to a claim that only the objectivist has made a normative claim and the "deliberative" theorist has, rather, much like the "Humean", only referred to some "facts" and taken these "facts" to be irreducible. And that doesn't describe any kind of deliberative view of procedural rationality. It is not the claim made by those who adopt a procedural view of deliberation that it is only a "matter of fact" that some things emerge as rightly chosen after reflection and nor is it their claim that what so emerges does so as a result of a psychologistic kind concerning the structure of reasons. Both kinds of commitment, whilst possibly held by a "Humean", are certainly not held by someone who takes deliberative rationality to involve central procedural constraints.
This is seen most clearly in the "Kantian" view that Parfit referred to in the early 2008 version of his work that Smith saw but which appears not to now be in the public domain. On that view the appeal made to systematic coherence rested upon a prior view about universalisation and universalisation is not itself a peculiarly psychological process and nor do its results only emerge factually without normative status. The point about such a process of universalisation is precisely that it provides, starting from a "thin" commitment, some substantive results. (Smith rightly emphasizes this in his reply to Parfit despite having sceptical doubts himself concerning the Kantian claim.)
To conflate this claim with the "Humean" commitment to psychologism and hence to make the view of Korsgaard and Rawls "subjective" in the sense of involving an implied form of internalism is a serious error in terms of rendition of Kantian accounts of reasons for action. Smith's criticism of Parfit in terms of the latter's failure to see that you could, if committed to a Kantian view, take it to be the case that substantive principles follow from procedural ones, seems to me correct. The point Smith does not make, and that I would, is that it is not at all obvious either that commitment to a Kantian view involves internalism (though some of Korsgaard's statements suggest that she, at least, can be careless in this regard).
Like Smith I also take it to be the case that the distinction between substantive and procedural views is less informative than Parfit thinks though, unlike Smith, I don't think it has no value. It has the value, as Parfit correctly brings out, of indicating the pattern of justifications and this pattern is at least part of what is at issue. But Parfit fails to see that substantive principles can be justified by procedural ones and also does not comprehend that procedural rationality need not involve psychologistic internalism.