A crucial consideration is a consideration that warrants a major reassessment of a cause or intervention.
Besides introducing the concept of a crucial consideration, Bostrom introduced two other concepts closely related to it. First, the concept a crucial consideration component, or a consideration that is not itself a crucial consideration, but which has the potential to become one when conjoined with additional considerations still unknown. As Bostrom writes, a crucial consideration component is "the kind of thing of which we would say: 'This looks really intriguing, this could be important; I’m not really sure what to make of it at the moment.' On its own, maybe it doesn’t tell us anything, but maybe there’s another piece that, when combined, will somehow yield an important result."
Second, the concept of a deliberation ladder, or a sequence of crucial considerations resulting in successive reassessments of the same cause or intervention. Consider, for illustration, an altruist who initially becomes a vegan out of concern for the treatment of animals in factory farms. Later, this person is exposed to the logic of the larder and concludes that consuming animal products is permissible because it increases the total number of animals. Finally, the altruist comes to believe that farm animal welfare is net negative and reverts to a vegan diet, reasoning that, since demand for animal products increases animals in expectation, it also increases net suffering. Many additional "deliberation ladders" can be imagined, related to the impact of meat consumption on the number of animals who feed on other animals, on climate change and its effects on wild animals, on public perception of the moral status of nonhuman animals, and on other considerations.
The potential existence of yet undiscovered crucial considerations raises a very serious challenge for any attempt to do good effectively on a large scale. As Bostrom writes, "Our noblest and most carefully considered attempts to effect change in the world might well be pushing things further away from where they ought to be. Perhaps around the corner lurks some crucial consideration that we have ignored, such that if we thought of it and were able to accord it its due weight in our reasoning, it would convince us that our guiding beliefs and our struggles to date had been orthogonal or worse to the direction that would then come to appear to us as the right one." Such a challenge is particularly serious for longtermists: the additional difficulty associated with trying to influence the far future, and the greater neglect of this area until very recently, strongly suggest that relevant crucial considerations remain undiscovered....