I don't think that Smith or Brown understood what Clement found offensive about the heretics he calls 'the Carpocratians' in the Letter to Theodore and the Third Book of the Stromateis (and left unnamed in Book Seven Chapter 16). The closing words of the Stromateis make clear that they were rejecting the canonical gospel of Mark, lumping it together with the 'prophetic writings' which came before the advent of the (true) Gospel commonly referenced as 'the secret gospel' or 'mystic gospel' by contemporary scholarship on the Letter to Theodore.
I am not sure that μυστικός was a formal name of the text. My guess is that it is the same text that Clement references throughout his writings as 'the Gospel.' Clement is just calling it μυστικός because he imitating the language of the heretics (cf. Irenaeus 1.13.1).
In any event, to save everyone the suspense it is clear from Strom 7.16 (which bears a striking resemblance to the arguments in to Theodore) that the heretics are being criticized by Clement for developing 'dogma' without going through the necessary 'training' through the prophetic writings and then the canonical gospels. In other words, they rely only on the 'mystic' gospel and as such - at least according to Clement - develop dogmas and interpretations which result from mere human understanding.
The reason I bring this up is because there has been a lot of speculation - based on the 'fuzziness' inherent in the existing translations, whether Carpocrates actually altered the wording of the commonly held gospel. In other words, when Clement says this:
But since the foul demons are always devising destruction for the race of men, Carpocrates, instructed by them and using deceitful arts, so enslaved a certain presbyter of the church in Alexandria that he got from him a copy of the secret Gospel, which he both interpreted according to his blasphemous and carnal doctrine and, moreover, polluted, mixing with the spotless and holy words utterly shameless lies. From this mixture is drawn off the teaching of the Carpocratians. (Morton Smith translation)
Brown's translation is basically the same. Many modern commentators have supposed that the 'pollution' that Carpocrates might have involved some alteration to the original document.
Yet my reading of Stromateis 7.16 leads me to the conclude that a few choices that Morton Smith while rendering the original Greek into English unnecessarily muddied the waters. For instance, the word 'interpreted' can have a lot of meaning. A writer is generally understood to 'interpret' experience in his writings so some have supposed that Carpocrates has 're-interpreted' the original gospel. But this is not what is meant here.
The original Greek word here is ἐξηγήσατο. Josephus used 1834 eksegeomai as a "technical term for the interpretation of the law as practiced by the rabbinate" (A. Schlatter, Der Evangelist Johannes, Stuttgart, 1948, p 36, who cites Josephus, Ant. 17.149; War 1.649; 2.162). Our English word exegesis develops from the original terminology. So whst Clement is criticizing is the heretical interpretation of a commonly held gospel.
I don't know what is a preferable English terminology. I am not a translator obviously. One might think however of John 1.28 and its use of the same word which is commonly rendered in English Bibles as 'declared' - i.e. "No one has seen God at any time. The one and only Son, who is in the bosom of the Father, he has declared him." Acts 15.14 translates the same term as 'reported.' The point again is that we are dealing only with an interpretation of a commonly held text.
Then we move on to the second half of the same section where the choice of terminology is even more unusual. Carpocrates not only 'interpreted' the original gospel but somehow 'polluted (it), mixing with the spotless and holy words utterly shameless lies. From this mixture is drawn off the teaching of the Carpocratians.' I have met many people who have drawn the same misguided inference from these words that Carpocrates somehow 'tampered' with the original gospel.
I really take issue with the rendering of 'pollution' and 'mixture' for the original Greek words ἐμίανε and ἀναμιγνύς. The actual meaning of ἐμίανε is 'stained' or 'soiled.' Something stained or soiled can have the derived meaning of 'polluted' but given that the next word also literally means 'unsoiled' or 'untouched' it is strange that both men would go away from the original sense.
That Smith would have chosen the English word 'mixture' for ἀναμιγνύς in my mind demonstrates that he was deliberately avoiding 'sexing up' the text. For the term ἀναμίσγω actually means 'to have (sexual) intercourse' according to Liddell. He uses many examples to show this including Herodotus's account of Babylonian ritual prostitution "The foulest Babylonian custom is that which compels every woman of the land to sit in the temple of Aphrodite and have intercourse with some stranger once in her life." There are other signs in the sentence that Clement means 'sexual mixture' - note the reference to 'carnal.'
I also take issue with the translation of Καρποκρατιανῶν δόγμα to mean 'the teachings of the Carpocratians.' Strom 7.16 demonstrates quite clearly that Clement is taking issue with the Alexandrian heretics for their dogma - i.e. their officially held beliefs and practices. As such, in the same way δόγμα should be rendered as 'dogma.'
It is also important to note that the original word order in Greek is slightly different which again helps clear up the misunderstanding about Carpocrates tampering with the commonly held Gospel:
Carpocrates so enslaved a certain presbyter of the church in Alexandria that he got from him a copy of the secret Gospel, which he both explained according to his blasphemous and carnal opinion and, moreover stained - the unstained (ἀχράντοι) and holy words utterly having intercourse with shameless lies. From this mixture is drawn off the Carpocratian dogma.
The point thus is that, as we see in Stromata 3.1 - 10 (with the Carpocratians named) and Stromata 7.16 with the unnamed. The same gospel text is interpreted according to a heretical (and supposedly highly sexualized) dogma. Yet as Clement makes clear in Strom. 7.16 - the heretics clearly did not alter the contents of that commonly-held gospel.
