A non-moral 'fact of reason'

If we allow for the adequacy of the 'fact of reason', understood as the consciousness of the bindingness of the moral law, then it appears that we must equally admit the possibility of a fact of reason based on the commands of non-moral reason. Why does it have to be a fact of practical reason, rather than simply any fact of reason, such as a fact of theoretical reason? Like we can be conscious of the bindingness of the moral law, so we can be conscious of the bindingness of non-moral reasons, as for example in the case of mathematics. If the necessity of the bindingness is sufficient to establish the reality of freedom in the one case, then it should also be sufficient in the other case. I think that Allison's claim is correct that if considerations of rational agency cannot do the job, then no appeal to specifically moral considerations could change this. "[I]t must be insisted that if the general argument from the presuppositions of rational agency fails to provide adequate support for an incompatibilist conception of freedom, then no subsequent appeals to specifically moral requirements or `facts' could conceivably do the job. Basically, this is because any claim to the effect that our general capacity to act on the basis of principles, frame ends or incorporate incentives etc. can be adequately accounted for in a naturalistic, causal fashion could easily be extended to our presumed capacity to act from duty alone." (Allison: 1996, p. 125)