The ten commandments were revealed by Moses coming down from the mountain, and presented to Israel on two tablets – why two tablets? When Jesus was asked what the greatest commandment was, he responded by giving a twofold answer; “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the greatest and first commandment. And a second is like it: You shall love your neighbour as yourself. On these two commandments hang all the law and the prophets’” (Matthew 22:38-40). The parallelism is not a coincidence. As the Catechism of the Catholic Church says:
When someone asks him, “Which commandment in the Law is the greatest?” Jesus replies: “You shall love the Lord your God with all your heart, and with all your soul, and with all your mind. This is the greatest and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments hang all the Law and the prophets.” The Decalogue must be interpreted in light of this twofold yet single commandment of love, the fullness of the Law:
The commandments: “You shall not commit adultery, You shall not kill, You shall not steal, You shall not covet,” and any other commandment, are summed up in this sentence: “You shall love your neighbor as yourself.” Love does no wrong to a neighbor; therefore love is the fulfilling of the law.
Classically or ‘traditionally’, it has been thought in Christian tradition that the first three commandments were on the first stone tablet, whereas the final seven were on the second, precisely because the first three are all to the same effect, namely, as the שׁמע (Shemah) says: “You shall love the Lord your God with all your heart, and with all your soul, and with all your might” (Deuteronomy 6:5). The last seven commandments, on the second tablet, therefore, are all to the complimentary effect of “thou shalt love thy neighbor as thyself” (Leviticus 19:18). What Jesus was doing, therefore, when he answered as he did, was to sum up the law (תּורה), not only in referring to it, but in referring to the quintessence of the Decalogue itself, of which all the other 613 commandments of the Torah were extrapolations. All the commandments of the Torah are reducible to the ten commandments, and the ten commandments on the two tablets are reducible to Jesus’ twofold elucidation of The Greatest Commandment.
In the Medieval period, the Scholastics were anything but unaware of, or uninterested in, issues of the relationship between the divine law and natural law, and how to best interpret the Decalogue in light of natural law theory, given the presumption that the first tablet contained the first three commandments, and the second contained the other seven, so that Jesus’ answer reflected an awareness of this division of ‘words’ (Decalogue literally means ten ‘words’). In particular the question which Medieval Philosophers addressed was whether any of the ten commandments allowed for dispensations, such that under certain conditions it was not immoral to disobey them. For instance, if the ten commandments are all expressions of natural law, and at least one commandment stipulates that ‘one shall not kill’, but God has killed some people, then either God has acted immorally, or there are some exceptions to the rule as it was laid down. Blessed John Duns Scotus, the Doctor Subtilis, thought that the first three laws were indispensable, but that the other laws on the second tablet were extensions of natural law for which some dispensations may exist which would excuse one from having to obey them.
To the question, then, I say that some things can be said to belong to the law of nature in two ways: One way is as ﬁrst practical principles known from their terms or as conclusions necessarily entailed by them. These are said to belong to the natural law in the strictest sense, and there can be no dispensation in their regard, as the argument for the ﬁrst opinion proves. It is to these that the canon of the Decrees of Gratian refers, where it is said that “the natural law begins from the very beginnings of rational creatures, nor does time change it, but it is immutably permanent” – and this I concede. But this is not the case when we speak in general of all the precepts of the second table [of the decalogue]. For the reasons behind the commands and prohibitions there are not practical principles that are necessary in an unqualiﬁed sense, nor are they simply necessary conclusions from such. For they contain no goodness such as is necessarily prescribed for attaining the goodness of the ultimate end, nor in what is forbidden is there such malice as would turn one away necessarily from the last end, for even if the good found in these maxims were not commanded, the last end [of man as union with God] could still be loved and attained, whereas if the evil proscribed by them were not forbidden, it would still be consistent with the acquisition of the ultimate end. But it is different with the precepts of the ﬁrst table, because these regard God immediately as object. Indeed the ﬁrst two, if they be understood in a purely negative sense – i.e., “You shall not have other gods before me” and “You shall not take the name of the Lord, your God, in vain,” i.e., “You should show no irreverence to God” – belong to the natural law, taking law of nature strictly, for this follows necessarily: “If God exists, then he alone must be loved as God.” It likewise follows that nothing else must be worshiped as God, nor must any irreverence be shown to him. Consequently, God could not dispense in regard to these so that someone could do the opposite of what this or that prohibits. (In support of this put the two authorities here that are found in Richard, ch. 5.) The third commandment of the ﬁrst table is that which concerns the observance of the Sabbath. It is afﬁrmative insofar as it prescribes that some worship be given to God at a speciﬁc time, but so far as the speciﬁcation to this or that time goes, it does not pertain to the law of nature strictly speaking. Similarly with the negative portion included therein, which forbids servile work for a deﬁnite time that would interfere with the worship to be shown to him. For such work is only prohibited because it impedes or keeps one from the cult that is commanded.
~Bl. John Duns Scotus, Ordinatio III, suppl., dist. 37
St. Thomas Aquinas, the Angelic Doctor, thought, on the contrary, that all ten commandments were expressions of natural law and that, properly understood, none of them were truly dispensable. For instance, as St. Thomas read it, the commandment stipulating that ‘thou shalt not kill’ is best understood as ‘one shall not murder’ or kill wantonly. William of Ockham, who, being a nominalist, ironically has not been remembered by any endearing name in Catholic tradition (though he is well remembered for Occam’s razor), was a voluntarist (the equivalent, in Ethics, to nominalism in Metaphysics), and as such he suggested that all ten commandments were dispensable if only God had decided to suspend them or supersede them.