Valuation: Its Nature and Laws, Being an Introduction to the General Theory of Value
The Intelligible World: Metaphysics and Value
Fundamentals of Ethics: An Introduction to Moral Philosophy
Humanity and Deity
Here's a quote from one of his books that I couldn't find online, Beyond Realism and Idealism.
The main issue then, from which this entire discussion started, and which is involved in the modern identification of realism with naturalism, is the contention that, since reality is prior to knowledge, mind must consequently (italics mine) have a status which is derivative and not pivotal. Why this, consequently, should ever have entered into modern thinking I am at a loss to see. It does not at all follow that, because the principle of being, or the postulate of antecedent reality, is dialectically necessary for an intelligible theory of knowledge, the mind that knows is causally derivative from this antecedent, being conceived as nature in the sense of modern science. This derivative status of mind and knowledge does not follow from the epistemological postulate of realism but is rather an inference, whether rightly or wrongly made, from a specific scientific theory, namely, that of Darwinian evolutionism.
It is natural to want to take the evolutionary picture at its face value, with all that it involves for human knowledge. But we have seen that this naturalistic account does not go very far, and that, when pressed too far, tends to become something 'perverse --' for it, denatures mind and with it the knowledge which it is the minds function to achieve. Such an account makes of the Sermon on the Mount as much of an accident as the Ninth Symphony and of Newton's Principia an even greater anomaly, perhaps, than both.
To the 'transcendentalists' who demur at this perverseness it is pointed out that, after all, it is imply a matter of historical fact that thinking and reasoning man did evolve by natural processes from anthropoid ancestors, a fact not disputed even by those whose deepest feelings are opposed to the admission. But so long as mystery surrounds the manner of the evolution there will always be the refuge of ignorance for the transcendentalists. To me this seems clearly a case of ignoratio elenchi. The issue here is not one of historical fact, although even on this count, the phrases 'historical fact' and 'evolve by natural processes' are both too ambiguous to say whether the above proposition is or is not disputed; in some interpretations it certainly is. The issue is not whether man actually evolved; the question at issue is whether natural processes, in the sense conceived by natural science, can account for mind and intelligence as presupposed by natural science itself. We have here that same logical confusion characteristic of all naturalistic accounts of knowledge. First, various natural sciences are taken as premises for the conclusion that the objects or contents of consciousness occur within the organism as part of the response to stimulation by physical objects other than it. Then we are told that these intra-organic contents have a cognitive function. But how ascribe to these mere contents functions which, by their very nature, they are patently incapable of discharging? This is the pons assinorum which no purely naturalistic account of mind has been able to cross. Or, making use of a figure often employed in this connection, by this supposed 'scientific' account of knowledge, the scientist himself cuts off the very limb upon which he sits. For in thus deriving mind and knowledge from nature, as science conceives it, he must assume that his own account of nature is true. But on his premises, the truth of this account, like that of any other bit of knowledge, is merely the function of the adjustment of the organism to its environment, and thus has no more significance than any other adjustment. Its sole value is its survival value. This entire conception of knowledge refutes itself and is, therefore, widersinnig. The fact that so many modern minds do not feel difficulties of this sort is one of the things I have never been able to understand. I can only surmise that our devotion to so-called empiricism has robbed us of all sense of logicality, or what I should call the finer inner harmonies of thought -- in short, the sense for philosophical intelligibility.
As to the transcendentalists, their belief in the transcendental character of mind is not the refuge of ignorance, but rather the result of their realization of the peculiarly vicious circle involved in all naturalistic accounts of knowledge. It is not their feelings that are outraged but their intellects.
A few pages prior to this, he claimed that "The derivative status of mind is the characteristic feature of all forms of naturalism." If this is the case, then this argument -- very similar to C. S. Lewis's Argument from Reason and Alvin Plantinga's Evolutionary Argument against Naturalism -- would seem to apply to "all forms of naturalism." In fact, Urban's statement that "The fact that so many modern minds do not feel difficulties of this sort" is very similar to Lewis's statement "the fact that when you put it to many scientists, far from having an answer, they seem not even to understand what the difficulty is" in his essay "Is Theology Poetry?" in The Weight of Glory and Other Addresses. Urban also used a similar argument in chapter 17 of Fundamentals of Ethics.