What does Buddhism add to a Stoic?

Well, that dialog reminds me of two stories.

This bit of your dialog:

Stoic: what? Is any man able to make you assent to that which is false or compel you to desire what you do not wish?

Buddhist: No

Stoic: In the matter of assent and desire then you are free from hindrance and obstruction?

Buddhist: Yes

Reminds me of a Zen story called "Nothing Exists".

82. Nothing Exists

Yamaoka Tesshu, as a young student of Zen, visited one master after another. He called upon Dokuon of Shokoku.

Desiring to show his attainment, he said: "The mind, Buddha, and sentient beings, after all, do not exist. The true nature of phenomena is emptiness. There is no realization, no delusion, no sage, no mediocrity. There is no giving and nothing to be received."

Dokuon, who was smoking quietly, said nothing. Suddenly he whacked Yamaoka with his bamboo pipe. This made the youth quite angry.

"If nothing exists," inquired Dokuon, "where did this anger come from?"

Perhaps I'm not supposed to explain it, but the way I read it is that Buddhism (though I'm not sure about Zen Buddhism) identifies various hindrances or fetters, of which maybe "anger" is one. Buddhist teaching (including e.g. the doctrine of "emptiness") is intended to help people escape these fetters.

In this story the student is claiming "attainment", i.e. he's claiming to realize that things are empty, perhaps implicitly claiming that by his realization (of emptiness) he has attained freedom (from fetters).

The teacher's action shows (teaches) that it's not enough to just say that things are empty: the youth's pride and self-protection ("self-love") remain as a seed from which anger can arise.

Similarly in your story you have the Buddhist claim that he's immune to coercion, free from hindrance, etc., which I think begs the question: because part of the purpose of Buddhism is to develop such freedom, and Buddhism doesn't take for granted that people already have that freedom which maybe your Stoic is trying to claim.

Your Stoic is maybe describing an ideal, an ultimate end. The Buddha (Buddhism, Buddhist Dharma) describes the present non-ideal (suffering) situation, and outlines a way towards the end.

The Stoic's claim, as stated, might be a bit naive, too, if you analyze it; for example:

• "to desire what you do not wish" might be a paradox (logically impossible), but IMO there are real-life examples of desires that make people unhappy, and of addictions etc.
• In the phrase "you are free from hindrance" it presumes that "free from hindrance" and "you" can coexist; whereas perhaps "you" (i.e. a sense of self) is a type of attachment, and maybe "free from hindrance" starts when the sense of "you" stops.

The latter part of your dialog starts with:

Stoic: Sir, it’s my soul.

And ends with:

Buddhist: Perhaps you will understand if you look at it from another angle. Answer my question, by acting virtuously and by wisdom you are training the will towards the good?

Stoic: Yes

Here the topic has been focused on "self" and "my" and "soul" and "one" and so on, rather than on the previous hindrances-versus-freedom dichotomy.

Well on that subject I think that Buddhism has at least two things to say about "self".

1. One is that a sense of self, or a self-view, or selfishness, is a cause of suffering.

   Alagaddupama Sutta (MN 22)

   23. "You may well accept, monks, the assumption of a self-theory[27] from the acceptance of which there would not arise sorrow and lamentation, pain, grief, and despair. (But) do you see, monks, any such assumption of a self-theory?" — "No, Lord." — "Well, monks, I, too, do not see any such assumption of a self-theory from the acceptance of which there would not arise sorrow and lamentation, pain, grief and despair."

2. When it (the sense of self) is used towards the good (which your Stoic seems to be suggesting, "by wisdom I train my will towards the good"), I think that Buddhism maybe calls this type of sense-of-self, "conceit".

   Conceit is a subject of the answers to this question: How are 'conceit' and 'identity-view' not the same? which includes for example:

   If one is better than someone and he thinks "I am better", or "I am equal" or "I am not as good" it is conceit. If the person is equal and he thinks: "I am better" or "I am equal" or "I am not as good", it is conceit". If the person is not as good and he thinks: "I am better" or "I am equal" or "I am not as good", it is conceit. - it should be 9 permutations rather than levels.. I couldn't find the sutta to link it. I just remembered it.

   Conceit is also mentioned in this sutta (AN 4.159):

   'This body comes into being through conceit. And yet it is by relying on conceit that conceit is to be abandoned.' Thus was it said. And in reference to what was it said? There is the case, sister, where a monk hears, 'The monk named such-and-such, they say, through the ending of the fermentations, has entered & remains in the fermentation-free awareness-release & discernment-release, having known & realized them for himself in the here & now.' The thought occurs to him, 'The monk named such-and-such, they say, through the ending of the fermentations, has entered & remains in the fermentation-free awareness-release & discernment-release, having known & realized them for himself in the here & now. Then why not me?' Then he eventually abandons conceit, having relied on conceit. 'This body comes into being through conceit. And yet it is by relying on conceit that conceit is to be abandoned.' Thus was it said, and in reference to this was it said.

   It's a bit long but I think it's saying, "I have a conceit that I think I can be good: that I can be as good as someone else who was good or did well. The conceit itself isn't good, but by relying on it, etc."

   IMO there's a similar sutta (SN 51.15) about using desire to abandon desire.

In summary I think these are examples of what Buddhism can "add to" what your Stoic was saying?

I'm not sure why the Stoic introduced "self" into the conversation at all. Buddhism too talks about Wisdom and Intention (e.g. "Right Intention", etc.), but maybe (at least initially) without claiming whether they are or are not mine.

I'm not sure what the purpose of the Stoic's "soul" (or theory of soul) is. I guess its purpose is to identify with eternal/divine virtues, which I more or less ignorantly attribute to piety of the Ancient Greeks (who I imagine saying that Man isn't good but that some men embody some godly virtues).

This is poorly made-up conversation to find the loophole of Buddhism teachings especially no self idea (Anatman) but actually it does not prove any strong self (Atta) existence. The answers of Buddhist must be written by non-Buddhist who studied Buddha's teachings superficially and on this particular point "The Act of Will" called Chanda in Buddhism should be "I" and with strong belief that Buddhism cannot deny Chanda is not "I" or "mine".

The person who learned Buddha's teachings properly will reply Stoic questions differently. It could be verbally written like below.

Stoic: Yes, if you attach yourself to what is not given you will sure suffer. These five aggregates you counted must have been something not in your power. Have you nothing which is in your own power, which depends on yourself only and cannot be taken from you, or have you any thing of the kind?

The answer should be - In Buddha's teachings there are only Sankhara Dhamma are occurring. There is none can be given to possess/control to be taken ownership. There is nothing a single person can possess (can tell this is mine, I am controlling it, I am taking it with me indefinitely, I have power to control/manage how it behaves...).

Stoic: what? Is any man able to make you assent to that which is false or compel you to desire what you do not wish?

The answer should be - There is nothing can be called as "You" or "I" in here. In this Sankhara world where one person verbally say to another person to understand each other as we called people "Mr. or Mrs./Ms. A", "Mr. or Mrs./Ms. B", A can ask B to do something and vice versa. So called you ask so called me to do something and vice versa. This is the case. There is another case A does something on A's own desire/will/Chanda. This is the second case. Chanda is one of Nama Kaya and it is not permanent/eternal, not able to be possessed. It is one of Nama Kaya originated from Avidya (in plain English Ignorance). Because of this Ignorance a person viewed as Chanda/Will is mine, I did my Chanda to happen, I have Chanda therefore I am,...But in a period of single day, there are many countable obvious Chanda(s) happened and extinguished as well as many delicate Chanda(s) where a very good mindfulness and concentration require to notice them.

Stoic: In the matter of assent and desire then you are free from hindrance and obstruction?

This is something backing up the religions in which people believe there is god/creator/ruler (details below). In Buddha's teachings Avidya/Ignorance lead Citta Sinkhara (I memorize, I suffer) eventually lead to Chanda/Will/Desire. In proper Buddha's teachings we do not say my Chanda/Will/Desire. Laypeople (one who didn't get any attainment to be enlightened) with Atta Samjna(the perception of existence of "Self" which has either eternal or being controllable/possess-able or both) see the mind is "Self" (I think therefore I am/I desire therefore I am). But in Buddha's teachings there is no such entity callable "Self".

The idea of "Act of will"/Will/Free Will is originated from religions of God(s). For the early believers of God, everything is under God's will. But modern people found that is dangerous and outlaw idea. If someone burn other people or bomb a group of people to death/injured and that person says it is God's will then religion of such people does not help very much about the damage in both physical and ethical. So new civilized people invented a things called Free Will or Will of people which is separated from God's will. By doing so God is relieved from inappropriate responsibility of a single person wrong doing as well as ethical and legal constraint can posted and it is publicly and religiously acceptable. It is obvious that Physical Bodies (Rupa Khandha) is Anatta (not Atta) for Westerners (Middle easterners and Mediterraneans of early Buddhism ages) but they do not fully understand other four Khandhas (Vedana, Samjna, Sankhara, Vijnana Khandas) or called soul to one of them. So all four Khandas combined to a word called mind or soul and they thought there is a chance to find a loophole of Anatta (no self, no Atta) of Buddha's teachings because they failed to notice the latches and couplers between two consecutive transitions of state of mind since Citta Khandas very short-lived and very fast. Only the trained person to do Vipasana with strong concentration can see the details transitions of Nama Kaya.

There are many anatman definitions and explanations in Buddhism literature both printed and web but here is concise repetition here.

I see, therefore I am.

No, I see because I have eyes and things to views. When these two contact I have a sequence of thinking, memorizing, examining and judging occurs in my mind. Seeing doesn't prove it is me

I hear, therefore I am.

...As above seeing

I smell, therefore I am

I can taste, therefore I am

I can feel the touch, therefore I am ...all as above seeing

I think, therefore I am the contact of things memorized and mind makes thinking, judging and examining mentally and all phases are temporary, not controllable, not possess-able and extinguished/depleted eventually. In every steps and phases of transitions of state of mind (or called soul) a properly taught Buddhist cannot find Atta Samjna (the idea of perception of self). That is true, all mental bodies (four Khandas, Vedana/suffer, Samjna/memorize/percept, Sankhara/initiate/encourage/activate, Vijnana/be conscious or called soul to one of four) are Anatta (not to be possessed, have an end, can deplete, can extinguish). Chanda is also Anatta in both wholesome desire/Chanda and unwholesome desire/Chanda.

Buddha said when a person is doing meditation or Vipasana only Samkhara Khanda is observing or insightfully viewing to other Samkhara Khanda. That means we cannot find I or Me or My or Mine even in doing meditation/Vipasana. Verbally we say I meditate, I do Vipasana but it is just for the sake of language and colloquial sayings. There is no such case that you are going to find any sixth Khanda or/and a Khanda that can be called "I", "Mine" or "Self" in Buddha's teaching or outside Buddha's teaching. This also applied to both external and internal from a viewpoint of a person's Khandas. So will/volition/Chanda or whatever Stoic called cannot be "I" or "Mine" because it has originated cause "Ignorance/Avidya" and other supporting factors which are not controllable/possess-able by a person. In conclusion, any Stoic or early/late philosopher cannot prove a single entity (in physical or metal form) that can be self (either can control/possess, persist, eternal, can be created, can be managed).

More or less the same for morality, just takes away Essence from the philosophy.

I don't know Stoicism well enough, but your question seems to wonder how to add something that somehow enhances Stoicism. This is the wrong approach.

Eg: rebirth is a central tenet of Buddhism IMHO, what does Stoicism say about that? Helping other, creating merit and virtue, cultivating the mind are central to Mahayana Buddhism AFAIK, what does Stoicism say about that? I feel that it's like a blip in the Buddhist map, like someone said.

Stoicism says that if you are suffering it is within your power to change your internal interpretation of the situation. I don't know much about Buddhism, but if most of life is suffering, then there is the opportunity to adjust your perspective in most of your life.

Stoicism is straight to the point, which is nice, but Buddhism covers a bit more territory. Also, Stoicism requires less etymology to understand.

There are a few kinds of attachments that cause mental anguish. Buddhism attempts to end all forms of this, plus increase insight and awareness, and allow one to experience different mental states, like jhanas.

So, for example, if someone insults Jane, an all too often reaction is for her to defend her identity, her values, what she owns, and what she thinks she is. This creates a lot of unnecessary stress, and this defensiveness can turn into an argument.

Buddhism aims to increase empathy and compassion, decreasing conflict: By understanding ourselves we understand the world better. This in turn removes conflict and ill-will, removing unnecessary stress.

Buddhism aims to remove mana, which is a kind of comparison that creates jealousy and hurt.

Eventually Buddhism overlaps with Stoicism, removing quite a bit of attachment. However, as far as I can tell that's where Stoicism mostly begins and ends. Buddhism gets to the point where new attachment is not created, so that there is no future suffering. However, I haven't seen anywhere in Stoicism going this far, only dissolving attachment once the suffering has started.

All in all, Stoicism and Buddhism do overlap, but Stoicism is a bit of a blip on the map.