With that build-up, let us consider the crucial datum, namely 10:1-3, with v. 2 as the primary evidentiary locus. In the NRSV, this passage reads as follows:
1 Since the law has only a shadow of the good things to come and not the true form of these realities, it can never, by the same sacrifices that are continually offered year after year, make perfect those who approach. 2 Otherwise, would they not have ceased being offered, since the worshipers, cleansed once for all, would no longer have any consciousness of sin? 3 But in these sacrifices there is a reminder of sin year after year.We must define carefully the argument being made by Robinson, and which I find incontestable. He is not arguing that Hebrews must be pre-70 because it talks about the Jerusalem temple as a present reality; he is quite aware that Jewish writers continued to do that for centuries after the destruction. No, the issue is the logic of the passage. Hebrews here is arguing the following:
If the sacrifices cleansed once for all, they would have ceased.Of course, one could quibble with Hebrews' logic on metaphysical or other such grounds, but that's quite beside the point. What matters is that the conditional is only satisfied prior to 70. The argument is sound prior to 70, unsound afterwards. More to the point, it is unsound in a way that would have made it ridiculous to advance the argument post-70. After the destruction of the temple 10:1-3 would have been, quite simply, a howler. All the reader had to say was "But Mr. Hebrews, the sacrifices have ceased." A post-70 Hebrews is an incomprehensible Hebrews.
The sacrifices have not ceased.
Therefore the sacrifices do not cleanse once for all.
Thus far so good. Where Robinson perhaps trips up is that he again exhibits symptoms of his severe Neronitis. Hebrews mentions persecution. It mentions greetings from "those from Italy" (13:24) which Robinson, probably correctly, interprets as indicative that Hebrews was not written in Rome, or anywhere else in Italy, despite hypotheses to the contrary: the language of being from Italy suggests that he was referencing persons who were not currently in Italy; instead, he suggests that it was written to Rome, a hypothesis about which I am less sanguine. So, he argues, it mentions persecution, it's written to Italy...well, surely it must be referencing the Neronian persecution but postdate the destruction of the temple, and thus should be situated in the late-60s. Moreover, he suggests that since it makes no mention of Paul, despite referring to Paul's companion Timothy in 13:23), it probably postdates Paul's death. Thus he dates it to c. 67. Now, 67 is a decent possibility. Certainly, there is nothing to exclude it. I do wonder however if Robinson's tendency to see Nero around every New Testament corner has perhaps led him too quickly to place this letter at this time.
A final word should be said about the inevitable speculation regarding authorship. This is a temptation too tantalizing to ignore in any critical discussion of Hebrews. Robinson argues that either Hebrews was written by Barnabas or by someone whose name no longer exists in our extant material (the latter is a possibility too oft ignored: we should not take for granted that the author is someone whose name we otherwise know). His argument is that disagreements about Hebrews' authorship were limited to the eastern church, whereas the western church only knew Barnabas as the author. He notes also that Hebrews was more prominent among western than eastern theologians in the early Patristic era, and thus surmises that they were better situated to know who wrote the text. I will confess that I have not undertaken the work to fact-check his claims on these matters, because the authorship of Hebrews is besides the point for my purposes. That said, if he is correct on these data, it would indeed be a strong argument, certainly stronger than speculating on the basis of the content and then trying to correlate with biographical details of known figures (for instance, the incredibly weak argument that since Hebrews has Platonic-sounding material, and since Apollos is from Alexandria, and since there was a known Middle Platonic Jewish philosopher active in Alexandria in the first-century, it must be Apollos. One cannot begin to parse out the logical fallacies is in this line of argumentation). Myself, I increasingly suspect that the very confusion over the author's identity suggests that it wasn't someone otherwise remembered in the early church, perhaps a figure close to Paul whose name was soon lost to history (the proximity to Paul accounting for the fact that already in the second century Hebrews is appearing in collections of Pauline writings). For my purposes, that is less important than the date, which is clearly pre-70 (and one might add, almost certainly post-50, as Acts 16 seems to indicate that Timothy did not become prominent in Christian ministry until around that time).