The philosophy of Aristotle makes many facts of reality plain as day. One such fact is the objective and subjective intent of, for instance, drinking tea.
Tea is a cause, and all causes have effects. Now if one wills to drink tea, then he objectively wills one of the effects, but the intent is unknowable with absolute certainty unless you have the knowledge of God.
What are the effects of tea? This depends on the definition of tea, and thus it is imperative that a just definition be found and kept. As someone who has also had tea, by my observations, tea is the drink made of water and the extract of plant leaves, so this is the cause we will analyze.
The effects of water are hydration. Man has no reason to drink water other than that it is necessary for his hydration. This is a part of tea.
The effects of tea extracts present in the water constituting said tea are subjectively defined by the choice of leaf, usually flavor as one such reason for choice, therefore the objective intent of choice of leaf is to obtain the effect of the choice of leaf.
We have considered the effects of the parts, but this was only to consider the effect of the whole which is the tea beverage itself, and is what informs us of the objective intent of drinking tea.
The effects of tea are hydration (from water), and effect of choice of leaf (from leaf). Now man desires the good in all things, or at least the appearance thereof, so there must be some benefit perceived from hydrating by this means which is greater than what is given by the parts individually; but we already, without specifying particulars of choice, have enough to determine the objective intent: the objective intent of drinking tea is to obtain the good of the effects therefrom, though what choice of effects are subjective, as is the why for the choice.
We may therefore conclude that you drink tea because you desire some good effect therefrom, whether accidental (to please oneself or others that one wishes to please), or essential (direct physiological effects).
So, when we apply this to the Jewish observance of the sabbath, we consider the following:
The Third Commandment: Remember that thou keep holy the sabbath day.
Now this is at least mentioned in Exodus and Deuteronomy, both part of the Jewish Torah, and first five books of the written Tradition of the Roman Catholic Church.
The effect of keeping a commandment is the obedience due to God. The effect of keeping this specific commandment is rendering to God the latria due to Him alone. Therefore the purpose of keeping the Sabbath in Judaism is these two effects, the former being the genus, and the latter being the species. That some Babylonian took it up “because it’s a good idea” or some other reason than observing the commandments doesn’t matter.
No authority is above reality, but exists to uphold reality. Insofar, therefore, as any authority rejects legitimate evidence or facts, especially that as from the the very object of study itself as the more deserving of esteem, and instead esteems something wholly extrinsic from the object itself without very good reason, is upholding his own fantasies as true over reality.
In all charity, I would like to point out that the only good reason to reject the Jewish Torah itself as the principal evidence for observance of the Sabbath is if there is just as strong evidence that information has been purposely obstructed just “to maintain distinctiveness”. The One True Church at that time certainly had no interest in being considered identical with any false religion, but the eighth commandment: Thou shalt not bear false witness against thy neighbor, is quite strong evidence to the contrary of obstructing the testimony thereof when the second commandment couldn’t be more clear that there is no borrowing implied anyways. One would therefore rightly assume from the reading of the verse itself that any Babylonian observance of “the Sabbath day” is a mere concomitant occurrence.