On Simon Blackburn's thought-invoking book "Ruling Passions: A Theory of Practical Reasoning" Michelle Mason wrote a clear and fair review that can be found here.
I summarise here her basic points and also jot down my views on this matter in square brackets.
Blackburn's Hume-friendly theory of pratical reasoning is different from both the oversimplified Humean instrumentalism and Kantian objectifying desire in an independent tribunal of reason. By presenting a fine-grained theory of deliberation, in which desire is also affected by deliberation, Blackburn strives to present Hume as non-relativistic. But even admitting this immense contribution, it is difficult to reconcile the traditional opposition between desire and reason, the perenial worry that prompts the entrechment of reason in various forms, most famously the Kantian school.
[I like Blackburn's move in general, that is, to provide a more sophisticated picture of Humean deliberation, which I believe has long been due to him. Yet I don't believe a thorough-going theory of this sort, like Blackburn's quasi-realism or that of Nagel to some extent, can provide the final answer. The tension between what Nagel calls the personal standpoint and the impersonal standpoint cuts deeper. Nagel's own insights on existentialist truth well illustrate this tension. Perhaps at the end of the day, we have no better option than being a Humean skeptic; or we could follow Hume in being a relentless and thorough philosopher on the one hand, and being a man that lives in common sense on the other. The pursuit of thorough coherence across all domains of human life and to encapsulate it into a grand system is perhaps as dogmatic as any blind dogma can go. Yet it seems that this impulse to systemise underlies most of the history of philosophy. On a theoretical level, a Pyhhronian suspension of judgement that is well learnt by Hume, which is negative in nature, is our only intellectually honest choice.]
