Dionysius “the Renegade”, of Heraclea (c. 330 – c. 250 BC) was a heterodox Stoic, a maverick Stoic, and presumably initially a student of Zeno, the founder of Stoicism.  You can read a short chapter about his life and thought in Diogenes Laertius.  Before becoming a Stoic he studied philosophy under the physicist Heraclides of Heraclea, the Megarian philosopher Alexinus of Elis, who we know was critical of Zeno of Citium, and under Menedemus, founder of the Eretrian school of philosophy, who appears to have studied under Stilpo and the Megarian school.  This tells us Dionysius was an experienced and eclectic student of philosophy before becoming a follower of Zeno, although he also apparently shared with Zeno a background in the Megarian philosophical tradition. We know he also studied poetry and literature and sought to imitate the great Stoic-influenced poet Aratus.

However, we’re told Dionysius broke away from Stoicism after suffering a painful bout of ophthalmia, inflammation of the eyes, and declared that pleasure (hedone) was the true goal (telos) of life and not an “indifferent” as Zeno claimed. His story shows that although Zeno was in a sense a highly eclectic philosopher, and Stoicism apparently tolerated some disagreement and debate, belief in the “indifference” of pain was considered an essential doctrine.  Once someone rejected that view it made no more sense for them to call themselves a “Stoic”.  This was probably in part because the doctrine of the indifference of pain was considered so central to Stoicism.  However, it was probably also because by arguing that “pleasure” is the true goal of life Dionysius effectively drew closer to the position held by rival schools of philosophy, such as the Cyrenaics and possibly the Epicureans.  Dionysius’ story suggests that he defined “pleasure” in part as the absence of physical pain.  Indeed, we’re told Dionysius left the Stoa to join the Cyrenaic school following his change of heart.  In his chapter on the life of Zeno, Diogenes Laertius says that:

When Dionysius the Renegade asked [Zeno], “Why am I the only pupil you do not correct?” the reply was, “Because I mistrust you.”

Diogenes Laertius also, listing famous students of Zeno, includes:

Dionysius, who became a renegade to the doctrine of pleasure, for owing to the severity of his ophthalmia he had no longer the nerve to call pain a thing indifferent: his native place was Heraclea.

We know little more about Dionysius.  He wrote two books on freedom from passions (apatheia), two on training exercises (askesis), four on pleasure (hedone), among others.  However, Diogenes Laertius also wrote in his account of Heraclides:

Again, Dionysius the Renegade, or, as some people call him, the “Spark,” when he wrote the Parthenopaeus, entitled it a play of Sophocles; and Heraclides, such was his credulity, in one of his own works drew upon this forged play as Sophoclean evidence.  Dionysius, on perceiving this, confessed what he had done; and, when the other denied the fact and would not believe him, called his attention to the acrostic which gave the name of Pancalus, of whom Dionysius was very fond. Heraclides was still unconvinced.  Such a thing, he said, might very well happen by chance.  To this Dionysius, “You will also find these lines:

a. An old monkey is not caught by a trap.

b. Oh yes, he’s caught at last, but it takes time.”

And this besides: “Heraclides is ignorant of letters and not ashamed of his ignorance.”