Were Those Living Before Sinai Really "Under Grace"?

It has been assumed by some that those living before the dispensation of the law at Sinai were "under grace" like those in this age (Rom. 6:14-15).  I have seen this assumption used to prove that tithing existed before the law (which it did--cf. Gen. 14:20; 28:22) "under grace," and therefore should be practiced now.  That's another study of its own, but I would like to raise the question as to whether people living before Sinai were truly "under grace." 

Now, it's evident that the grace of God spans the dispensations, but I believe that it's not manifested the same way and to the same degree in every age.  In no other age is grace said to "abound" and even "reign" like in the present one (Rom. 5:15, 17, 20-21).  True, "Noah found grace in the eyes of the LORD" (Gen. 6:8), but scripture doesn't say that he was "under grace" like a saint in this age.  God was gracious throughout the the old testament and told Moses this in no uncertain terms in Exodus 34:6-7, as they were communing together on Sinai.  Thus, God had shown himself gracious up to that point (Gen. 43:29), and will continue to do so through the ages, since that is part of his character (Ex. 22:27).  But I think to say that those living before the giving of the law at Sinai were "under grace" is erroneous.

Even though a written law was given at Sinai, there was an unwritten law that had been operative for about 2500 years:  the law written in men's hearts, the conscience (Rom. 2:14-15).  Adam and Eve acquired the knowledge of good and evil (i.e. conscience) upon their fall, and this knowledge was passed on, innately, to all of their offspring (Deut. 1:39; Rom. 7:9).  Hence, it is probably more correct to say that everyone living before the gospel of God's grace was revealed to Paul (Acts 20:24, Gal. 1:11-12) was "under law," either written or unwritten.  All of those living before Sinai, and the Gentiles living thereafter, were living under an unwritten law.  In some dispensational systems, the age between the fall and the flood is referred to as the "dispensation of conscience" (Scofield, Larkin, Chafer, et al.).  But conscience continues after the flood and after the written law is given to Israel, which distinguishes that people even further from the Gentiles than circumcision did (Deut. 4:8; Ps. 147:19-20).  From 1500 B.C. (Sinai) to Paul, the Gentiles were not "under grace" while Israel was under the law, were they?  Nor were they under the written law (Rom. 2:14; 1 Cor. 9:21). 

What clears this up, and the notion that everyone before Sinai was "under grace," is the understanding that, though the law may not have been written down until Sinai, it was operating within men, and God held them accountable for heeding it (Gen. 4:7; 2 Pt. 2:5).  Hence, the antediluvians were under law rather than under grace, albeit an unwritten law, as were Gentiles living while Israel was under the written law.

So, even though it may sound right that those living before the written law was given were "under grace," it's really not an accurate statement.  Those truly living "under grace" are the ones that the apostle Paul said were: believers in this age who have believed his gospel (Rom. 6:14-17) and entered the body of Christ thereby (Eph. 3:6).  As before, grace spans the dispensations because it's the character of God to be gracious, but technically only those saved in this present age by believing the gospel of grace are truly living "under grace."