This would not work very well to the Rambam (Maimonides) but I think this fits with Saadia Geon pretty well. And you can actually see this in the Gemara itself where mitzvot are assumed to have rational reasons that support them.
The problem is that the beliefs that people hold are determined by their self-interest, the synagogue they want to fit into, the self-image they want to maintain, and the desire to remain coherent with their past beliefs. People can deploy mechanisms to enable them to adopt and maintain their preferred beliefs, including giving a biased weighting of evidence; focusing their attention and energy on the arguments supporting their favored beliefs; collecting evidence only from sources they already agree with; and relying on subjective, speculative, and anecdotal claims as evidence for religious theories.
I want to claim that forming beliefs based on non rational methods is in itself against the Torah. This is at least implicit in the Rambam and the Сhovot Levavot (Duties of the Heart).
The Rambam considers the halacha process of the Talmud to be using reason to analyze and legal material that was received by tradition. The idea of the Geonim that the Talmud itself is received tradition he said was a very bad view--מְתֹעָב "disgusting" he called it.
Suppose I offer the opinion, "Colors are objective." What then is it that I am saying about colors? What I am saying is that colors are 'in the object.' In what object? In colored objects. What does "in" mean here? It means that a color - redness, say - is a property of the objects that are said to be red. That is, that the nature of those objects themselves and not anything else determines whether they are red or not. Hence, to say that morality is objective is to say that whether an action is right depends on the nature of that action; whether a person is good depends on the nature of that person; etc.
If one knows moral relativism to be true, then one cannot rationally believe any moral judgement. One cannot do so because in order to rationally believe something, the proposition must first be justified, and as a moral relativist you know that no moral proposition is true before you believe it, so you would not have any justification for accepting it.
So if moral values are objective, it is hard for me to imagine that the Torah would say to do otherwise. Rather we say we should keep Torah because it is good--it can't be measured against a standard of objective good. If it would be good by definition then saying "It is good" would be question begging. And this is how it is possible to analyze the Torah by reason as the Talmud does. Torah reveals what is good objectively, and the Talmud analyzes it. This leads to the type of understanding the Rambam had of Torah --a strong correlation between Torah and reason.
The sad thing about the lack of gentile understanding of the Talmud, is that it creates a situation in which they can't understand the Bible either because they don't know how to learn it with rigorous logic.
It seems to me that natural law [as some understand it] is not the same thing as the morality that we can perceive by reason. Natural law seems to imply that one who nature is to murder ought to murder since it is part of his nature. But the morality that can be perceived by reason says no.
Now you might complain to me that religious people are often not moral. That is because morality and spirituality are two separate areas of value. Each is perceivable of reason but they are two separate areas.