|Artistic impression of Epictetus|
with his crutch
One of the reasons for this, Long says, is that the work of ancient Stoics is far less accessible in its original and comprehensive form than the work of Plato, Aristotle, Epicurus, and Sextus Empericus. Only a few fragments of the work of the pre-Roman stoics is extant. It is the treatments of Stoic ethics by Roman scholars like Cicero, Seneca, Epictetus, and Marcus Aurelius that became influential during the Renaissance and Enlightenment, and are responsible for the traces of Stoic ideas that we find in Descartes, Spinoza, Leibniz, Rousseau, Grotius, Shaftesbury, Adam Smith, and Kant.
The development of Stoicism as a systematic philosophy was also hindered because of its core ideas getting assimilated in popular religious and philosophical movements.
Here’s an excerpt from Long’s essay:
In addition to the fragmentary state of the ancient sources, Stoicism was easily conflated or assimilated, on casual acquaintance, to ideas associated with the much more familiar names of Platonism and Aristotelianism. The conflation is not, of course, wholly mistaken. Outside metaphysics and technical logic, the three philosophies do have much in common, as the Academic Antiochus, Cicero’s friend and teacher, recognized. How easily they could be eclectically synthesized is particularly evident in the works of Philo of Alexandria, and even in Plotinus. This assimilation becomes still more complex in the writings of such early Christian thinkers as Origen, Tertullian, Clement of Alexandria, and Calcidius. Some Stoic doctrines, such as the identification of God with fire and the denial of the soul’s immortality, were anathema to the early Fathers of the Church – which helps to explain why no complete texts by any early Stoic philosophers have survived. But early Christianity appropriated a great deal of Stoic ethics without acknowledgment.Unlike Epicureanism, Stoicism has never been a monolithic church. Cicero, Seneca, Epictetus and Marcus Aurelius were creative in their own way—they disagreed with each other on many issues, and they developed their own opinions on various aspects their version of Stoic philosophy. Long points out that despite there being several major differences between Stoicism and Christianity, Stoic ethics and Christian ethics have been fully assimilated. So to a large extent Stoicism is now an unacknowledged part of the Christian tradition.