The author of the paper speculates that deontologists arrive at their belief via an emotional psychological process while consequentialists employ a more "cogni

The author of the paper speculates that deontologists arrive at their belief via an emotional psychological process while consequentialists employ a more "cognitive" process. But these observations of psychology, as you write, are unable to bridge the Is-Ought gap. Even when we can demonstrate how humans adopt beliefs, this does not by itself tell us if the beliefs are true. We cannot say "humans believe X" and then conclude "therefore X is true"; further we cannot say "humans believe X because Y therefore X is true" and likewise, and this is where the author errors, we cannot say "humans believe X because Y therefore X is not true". The author makes an interesting critique of Kant's system specifically but the question with regard to realism is if the rule itself is true. The author suggests the Is-Ought gap is true, writing that they do not intend to argue that "one can derive moral truths from scientific truths" (41). Instead they claim "scientific information can undermine factual assumptions on which moral thinking implicitly depends", using this premise to arrive at the formulation on 47 that just because we feel an emotional inclination, this may not correspond to an independent moral truth. This doesn't seem controversial. But the deontologist's thinking does not implicitly depend on the factual assumption 'what evolved is what is True'. The crux of the paper (47-48) is where the author suggests: 1. humans choose beliefs, often irrationally (no one denies this) 2. our judgments result from our emotional state (sure) 3. our emotions came from evolution (alright) 4. therefore it is unlikely there exists a coherent normative moral theory that can accommodate our moral intuitions (perhaps) 5. therefore "we have somehow crossed the infamous 'is'-'ought' divide" (no...not at all) Point 4, while possible, does not follow from Points 1-3, and Point 5 does not follow from Point 4. The author suggests they did not "attempt to derive an 'ought' from an 'is'" instead they merely "inferred...that the phenomenon of deontological philosophy is best explained as a rationalization of evolved emotional intuition [and, crucially, therefore false]." In other words, the argument is (A) deontology was adopted because of evolution (B) therefore deontology is not objectively true. But as you observe the author begins to feel discomfort at this (flawed) line of thought likely because it could apply to everything. As they write "If I care about my self only because I am biologically programmed to carry my genes into the future, should I stop caring about myself?". This is the horror of Empiricism. The author concludes that in addition to believing deontology is not true, they also view their own consequentialist principles as "not true" but as "the best", apparently we are to believe due to the reasoning given above. Ultimately the author appears to not understand what the Is-Ought Facts-Values problem actually implies: we are unable to make an observation about the empirical universe ("Humans have value to humans") and then conclude an objective value statement from it ("Therefore humans should value other humans").