[Do read Taleb's account even if you're not particularly interested in speculative philosophical histories, as his opening paragraph offers some great observations on poverty and elegance in India vs. The West, among other things, and there's a terrific excerpt from a Herman Hesse short story (in French) at the end of 94b.]
I agree with Taleb's assertion that the Syriac roots of many later Academy philosophers implies that the pre-Umayyad Levant was likely a center of a now-lost philosophical tradition. However, I think that the timeline offered by Taleb's evidence for Syriac import in the Greek philosophical tradition implies that this center may have been a product of Hellenization. One could plausibly argue that Neoplatonic thought was largely spearheaded by a Syrian tradition that existed in both Syria and Greece (Agathias attests to the Syrian influence in Athens; the lack of Syrian sources leaves an open question as to Syrian side of the equation). Perhaps there was an Apameia-Athens Axis in this period? Iamblichus founded a school in Apameia, where Numenius also practiced (and where Posidonius was born in the waning days of the heavily Hellenizing Selucid Empire). This idea of a Syrian-Greek philosophical axis fits with Taleb's suggestion that Greek was a lingua franca for Syrian intellectual life even during the Umayyad. Doesn't this imply the deep impact of Greek culture in Syria during the post- Alexander period? Taleb also points to the prevalence of Syrain skeptics to support his thesis. I'm not familiar with the specific skeptics he cites, but Pyrrhonism and Academic skepticism are both products of the Hellenized period.
The roots of this Syriac philosophical tradition could be from one of two sources: an already established Syrian philosophical tradition is fused into / incorporated within Greek traditions, or Greek cultural influence creates a philosophical tradition in Syria that draws on Syrian intellectual heritage while existing simultaneously under Greek and Syrian cultural umbrellas. The line between these two concepts is very close indeed, as all societies have implicit ontologies that can be found in (and grow from) language and social structure, and few societies find themselves without a philosophical tradition of some sort. What's perhaps most important are the mechanisms of transmission and incorporation, a process we can explore through one of Taleb's other examples: Pyrrho.
Taleb's note that "Pyrrho went east with Alexander & almost certainly encountered all the syncretistic systems developed there" is extended in note 94b, where Taleb 'traces' the notion of αταραξια (ataraxia) to the philosophical worldview of the "Orient." There's not much of a case made here for sourcing the concept; instead he explicates αταραξια via 2 stories: one in Arabic (which I cannot read) and another fragment from Hesse in French (which I recommend). Taleb's claim that this sort of knowledge seems irrevocably a part of his experience with Arabic wisdom strikes me as irrelevant to the source of this knowledge, an anecdote that says more about the legacy of these ideas than their source.
The task of actual conceptual sourcing is of course impossible, but we can establish a few basic principles of cultural transmission. First, we should remember that at certain moments in human history there are ideas that seem logically inevitable next steps. Human culture frequently finds itself addressing the same dilemmas even in distant locales. Secondly, we should note that cultural transmission invariably entails the work of translation in more than just a linguistic sense: concepts must be made to fit into different systems of knowledge than the one(s) from which they come. An idea lifted from one place may become something entirely new upon landing in a new one. The processes by which it changes are multiple, but I consider two main modes of change to be primary ones. The new cultural contexts may be different enough that a faithfully-rendered concept becomes something entirely new (as cinematic montage changes the meaning of shots by way of changing the surrounding material). Alternately, the mediator may be responsible for choosing methods of mediation that warp the original meaning and create a new set of contexts that would be new even in the original language and culture.
We can see the combined approaches of these first two methods of concept-transmission in the development of Christian religious ideology in the first 100 or 200 years after the death of Jesus. I'm referring to the way in which Christianity is a remolding of various ideas common in the mystery cults of the Graeco-Roman world. Most of these mystery cults themselves were products of this process, with roots in deities worshiped in conquered lands (though the resultant belief systems had little to do with the original beliefs associated with the deities). Early Christian iconography seems closely related to the iconography of Mithraism. The cult of Isis and that of the Magna Mater seem to prefigure the special roles assigned to the Virgin Mary. Resurrection is an important theme in these mystery religions (easily seen in the cults of Osiris, Attis, Adonis, Dionysis, etc). The Eucharist combines traditions of sacral kingship and theophagic rituals that entail eating the body of a fertility god. There was even a Christian defense of these prior practices as false imitators set forth by the devil through interpretation of the Hebrew Bible's prophetic references to Jesus. Justin Martyr, in his Dialogue with Trypho:
"For when they tell that Bacchus, son of Jupiter, was begotten by intercourse with Semele, and that he was the discoverer of the vine; and when they relate, that being torn in pieces, and having died, he rose again, and ascended to heaven; and when they introduce wine into his mysteries, do I not perceive that the devil has imitated the prophecy announced by the patriarch Jacob, and recorded by Moses?"It's also important to mention that these mystery cult beliefs - which were widespread throughout the Roman Empire of the early days of Christianity - lay a partial groundwork for conversion that helps Chrisitianity flourish, but that also effects Church doctrine as the Church hones its message to broaden its reach [think of the importance of the Council of Jerusalem in making Christianity available to the cultures of the Roman Empire].
Sandmel makes the point that these connections are not necessarily influences but perhaps natural expressions of tendencies of human mythmaking. All this implies the question: is Pyrrhonian αταραξια a philosophical 'discovery' common to humans, or is it (also) the product of a world of influences?
An excellent example of the third method of appropriation is the development of 20th Century philosophy in France, a story that 'begins' with Alexandre Kojève. Kojève (Kandinsky's nephew, incidentally) studied philosophy in Germany, where his major influences included Heidegger and Marx in addition to his primary interest in Hegel. From 1933 to 1939, Kojève lectured on Hegel's The Phenomenology of Spirit at the École Pratique des Hautes Études in Paris. For his seminar, Kojève translated Hegel himself, as well as translating on the fly from German to French during his lectures. Kojève's translations reflected an idiosyncratic post-Hegelian system of his own creation, combining a Marxist teleology with a rereading of Hegel using the vocabulary of Heideggerrian subjectivity (sadly, my notes on his rpecise chocie of words in French are not at hand). In fusing Heideggerrian terms to Hegelian ontology Kojève plants the seeds of postwar Continental philosophy in any number of directions: his students included Raymond Queneau, Georges Bataille, Maurice Merleau-Ponty, Andre Breton, Jean-Paul Sartre, Jacques Lacan and Raymond Aron, and his influence has also been cited by Derrida and Foucault. The encounter of these thinkers with Hegel (and Heidegger) via Kojève is a traceable root of many works by these thinkers.
Similarly, Pyrrho's return to Greece with a modified "Eastern" notion of αταραξια was a tremendous influence on later Greek thought, though not directly through Pyrrho. Pyrrho's influence was mainly felt after Aenesidemus's publication of the Pyrrhonian Discourses more than 200 years after Pyrrho's death. Likewise, it seems that Pyrrho's pupil Timon was mainly influential for his poetic and dramatic works - until his philosophical influence was picked up by Sextus Empiricus in the 2nd (?) Century AD.
Timon is an important stepping stone towards our quest for sourcing Pyrrhonian skepticism and the (translated) wisdom of "the East"; when Timon was asked by Aratus how to obtain the pure texts of Homer, he answered: "If we could find the old copies, and not those with modern emendations." We encounter the same problems not just with Syriac philosophical traditions, but also with the Greek, and with Pyrrho in particular. Pyrrho seems not to have written down his ideas (shades of Socrates); Timon, like Plato for his teacher, is the key written source for Pyrrho's later disciples.
Pyrrho's travels with Alexander's army led him to study with Indian Gymnosophists and Persian Magi. However, to attribute his knowledge to encounters with eastern philosophers seems misleading; Pyrrho's thought seems in many ways an extension of the skepticism of Zeno of Elea and the Sophists (a form of acatalepsia), combined with the Cynicism of Antisthenes (a precursor to ataraxia?). I find it plausible that his studies in the "East" allowed for a renewed approach toward the knowledge of his Greek philosophical tradition, and that his thought upon returning is a sort of reverse-Hellenistic syncretism - that is, a return of the foreign ideas to Greece in the form of already-existent Greek philosophical ideas. That these ideas are not picked up by the Greek philosophical tradition in earnest until centuries later adds another level of abstraction and cultural translation, but we should be aware that our contemporary view of the Greek and Asian philosophical traditions is colored by the incompleteness of our knowledge and the works now forever lost.
How did the Pyrrhonian skeptics arrive at their ideas of happiness and possible knowledge? We cannot know; we can only be happy that they did.