Stoicism has had a remarkable revival. Marcus Aurelius sells extraordinarily well, Epictetus is quoted in business books, and the vocabulary — dichotomy of control, amor fati, memento mori — has entered general use.
What circulates is a substantially reduced version, and the reductions are worth examining because they weren't arbitrary.
What the popular version keeps
The practical psychological techniques, mostly.
The distinction between what is and isn't within our control, and the instruction to concern ourselves only with the former.
Negative visualisation — deliberately contemplating loss to reduce attachment and increase appreciation.
The view from above, imagining oneself from a great distance to gain perspective.
Reflection on mortality as a way of clarifying priorities.
Emotional regulation through examining the judgements that produce emotions rather than the events themselves.
These are genuinely useful, they're the parts most compatible with a secular audience, and there's a documented historical relationship between them and modern cognitive therapy.
What it drops
The physics. Ancient Stoicism was a complete system with a cosmology. The universe was understood as a rational, ordered whole, pervaded by an organising principle — variously described as reason, nature or divine fire.
Accepting what happens wasn't a coping technique. It followed from the belief that events are part of a rational order, and that resisting them is resisting reason itself.
Remove that and "accept what you cannot control" becomes ordinary advice rather than a conclusion from a worldview.
The ethics. The central Stoic claim is that virtue is the only good. Not one good among several — the only one. Health, wealth, reputation and even life itself are classified as preferred indifferents: things reasonably pursued and which don't affect whether a life is good.
That's a radical position and it's the foundation of everything else. Equanimity in the face of loss follows from believing that what was lost wasn't a good in the first place.
The popular version generally retains the equanimity and quietly drops the claim that produces it.
The cosmopolitanism. Stoics held that all rational beings share in the same reason, which grounded a universal ethical obligation. Marcus Aurelius writes constantly about duty to others and about the community of rational beings.
A version focused on individual resilience and personal effectiveness has removed the social dimension almost entirely, which is a substantial alteration to a philosophy whose leading exponent was preoccupied with obligation.
Why the reduction matters
Not merely a question of historical accuracy.
Without the ethical framework, the techniques have no direction. Emotional regulation is instrumentally useful for any goal, including bad ones. The Stoics would have regarded a person who achieved perfect equanimity in the service of vice as having achieved nothing.
Without the physics, acceptance becomes resignation. The Stoic accepted events because they were part of a rational order. Accepting events because you can't change them is a different proposition, and it's considerably closer to fatalism than the original.
Without the social dimension, the philosophy becomes a technique for personal advantage, which is close to the opposite of a system built around duty to others.
The misused ideas
Two that circulate in distorted form.
The dichotomy of control is frequently read as licence to disengage from anything difficult. The Stoics were politically active — senators, advisers, an emperor — and Epictetus is explicit that we should act in the world while being unattached to outcomes. That's a considerably harder position than withdrawal.
Emotional suppression. The popular image of Stoicism as unfeeling is a misreading. The Stoics distinguished between the initial involuntary reaction — which they accepted as natural — and the judgement that follows. The aim was not to feel nothing but to avoid being governed by false judgements about what matters.
The honest question
Whether the techniques work without the framework is a genuine question rather than a rhetorical one.
The case for yes: cognitive therapy demonstrably works and doesn't require Stoic cosmology. Techniques can be separated from the theories that produced them.
The case for no: the techniques were developed as part of a practice aimed at a specific conception of the good life, and applied towards different ends they may be doing something different.
My own view is that the practical psychology transfers, that the ethical content is where the interesting material is, and that dropping it produces something that works fine and isn't Stoicism.
Where to start if you want the fuller version
The primary sources are short and readable, which is unusual for ancient philosophy.
Epictetus is the most practical and the most uncompromising. The Discourses are transcripts of teaching and read as such.
Marcus Aurelius wrote for himself and it shows — repetitive, personal, occasionally despairing, which is precisely what makes it valuable.
Seneca's letters are the most literary and the easiest entry point, with the complication that Seneca's life did not obviously match his advice, which he seems to have known.
Reading them directly rather than through summaries reveals a system considerably stranger and more demanding than the version in circulation.