Stoic Logic – Learning to Think Cleary and Live Wisely: Monthly Reflection

At our October meeting of Brisbane Stoics, around 40 people gathered at New Farm Library to explore a subject that rarely receives much attention in popular discussions of Stoicism: Stoic logic.

I had chosen this topic partly because it was an area of Stoic philosophy that I had personally neglected. Like many people, I had assumed that logic was likely to be a rather dry and difficult subject, concerned more with abstract arguments than the practical business of living well.

As it turned out, the subject proved surprisingly interesting. Our discussion moved from ancient philosophical puzzles to the Stoic understanding of the mind, and eventually to a question central to the whole Stoic project: how do we learn to judge our experiences correctly?

For the Stoics, logic was not simply an intellectual accomplishment. It was an essential part of the cultivation of wisdom.

The Stoics and the Problem of Truth

The ancient Stoics divided philosophy into three interconnected branches: logic, physics and ethics.

Logic, from the Greek logikē, encompassed much more than what we ordinarily mean by formal logic today. It concerned reason, language, argument, knowledge and the means by which we distinguish truth from error.

The early Stoics were particularly influenced by the Megarian school of philosophy, whose thinkers had developed a number of intriguing logical puzzles.

One of these thinkers, Eubulides, is associated with the famous Liar Paradox:

“This statement is false.”

If the statement is true, then what it says must be correct, making it false. But if it is false, then it seems to be telling the truth.

Another puzzle, the Heap Paradox, asks us to consider a single grain of sand.

One grain is clearly not a heap. Adding a second grain doesn’t seem to make it a heap either. But if adding one grain cannot transform something that is not a heap into a heap, at what point does a heap ever come into existence?

These puzzles might initially seem like little more than intellectual games. Yet they reveal something important about the limitations of language, the assumptions contained in our reasoning, and the difficulty of determining what is actually true.

The Stoics recognised that human beings are capable of error, and that these errors can have consequences far beyond philosophical argument.

If we are mistaken about what constitutes a good life, then even perfectly consistent reasoning might lead us in the wrong direction.

Chrysippus and Propositional Logic

Much of the development of Stoic logic is associated with Chrysippus, the third head of the Stoic school and one of its most influential thinkers.

Where Aristotle’s syllogistic logic largely examined relationships between categories or terms, the Stoics developed a sophisticated system concerned with relationships between complete propositions.

Consider a simple argument:

If it rains, the ground will become wet.

It is raining.

Therefore, the ground will become wet.

The conclusion follows from the premises because of the argument’s logical structure.

The Stoics examined several fundamental forms of such arguments, identifying patterns through which conclusions could be validly derived from propositions.

This distinction between logical form and the truth of the premises is especially important.

Consider another argument:

All bananas are fruit.

All fruit are purple.

Therefore, all bananas are purple.

The argument is logically valid. If the premises were true, the conclusion would necessarily follow.

But one of the premises is false.

Consequently, the argument does not establish a true conclusion, despite being logically valid.

This distinction offers an interesting insight into the Stoic understanding of psychological disturbance.

A person might reason quite consistently from a mistaken belief about what is good or bad, yet arrive at conclusions that undermine their wellbeing.

The problem is not necessarily that their reasoning is inconsistent.

The problem may be that they have accepted a false premise.

Impressions and the Judging Faculty

This brings us to what was perhaps the most important part of our discussion: the relationship between logic and Stoic psychology.

The Stoics understood human experience in terms of impressions (phantasiai).

As we encounter the world, impressions arise. In rational beings, these impressions can present content that is capable of being expressed as propositions—something that can be judged true or false.

The rational faculty can examine such impressions and either assent to them, reject them or suspend judgement.

For the Stoics, this capacity is central to human freedom and the development of virtue.

Consider a familiar example.

You return to your car and discover that someone has scratched it.

The initial impression might be expressed as:

Someone has scratched my car.

But almost immediately, another judgement may appear:

Someone has wronged me.

And perhaps another:

This is terrible. People have no respect. My day is ruined.

Notice what has happened.

An event has occurred, but the mind has begun adding interpretations and value judgements that go beyond the initial information.

Some of these interpretations might be reasonable. Others may be exaggerated, premature or mistaken.

The Stoic concern is not that we should ignore the damage or pretend that nothing has happened. Rather, we should examine the judgements through which the event acquires its significance.

Is this genuinely an evil?

Has my capacity to act wisely, justly or courageously been taken from me?

Or have I mistakenly elevated something external into a condition of my happiness?

This is where logic becomes a practical philosophical discipline.

The Passions and Mistaken Judgements

The Stoics believed that the passions (pathē) were closely connected with mistaken judgements about good and evil.

If we believe that something external is genuinely good, we may become consumed by the desire to obtain it or the fear of losing it.

If we believe that something external is genuinely evil, we may experience distress at its presence or fear at its anticipated arrival.

The psychological disturbance is therefore not simply a response to the external event. It is bound up with what we believe the event means for our wellbeing.

This is one reason the Stoics placed so much importance on learning to examine impressions.

Marcus Aurelius reminds himself in Meditations 8.49 not to add more to an impression than what it actually reports.

If someone tells us that another person has spoken badly of us, that is what we have been told. It does not necessarily follow that we have been harmed.

The additional judgement requires examination.

We might also consider how easily our minds construct arguments from questionable premises:

If this person disapproves of me, then I am diminished.

This person disapproves of me.

Therefore, I am diminished.

The reasoning follows a recognisable logical structure. Yet the first premise contains a questionable assumption about the nature of human worth.

A Stoic might challenge the premise itself.

Does another person’s opinion determine my worth? Or is my worth more properly connected with the character I cultivate and the way I conduct myself?

By examining the premises, we begin to change the conclusions we draw about our lives.

And with different judgements, different emotional possibilities become available.

Epictetus and the Testing of Impressions

Toward the end of our meeting, we turned to Epictetus’ Discourses, Book 1, Chapter 7, in which he defends the importance of studying logic.

Epictetus asks us to consider someone who wishes to avoid accepting counterfeit coins.

Is it sufficient simply to tell them to accept genuine coins and reject counterfeit ones?

Obviously not.

They must develop the knowledge and skill necessary to distinguish one from the other.

The same applies to our impressions.

It is not enough to tell ourselves to think correctly, accept what is true or reject what is false.

We must develop the capacity to recognise the difference.

Epictetus identifies three important tasks of reasoning: establishing what is true, rejecting what is false and suspending judgement when something remains uncertain.

These are not merely academic exercises.

Every day we encounter impressions that ask for our assent.

This person has insulted me.

I cannot cope with this.

I need this opportunity to be happy.

Something terrible is going to happen.

Each impression presents an opportunity to practise the art of judgement.

Is it true?

What evidence supports it?

Does the conclusion actually follow?

Have I confused something preferred with something genuinely good?

And sometimes, perhaps most importantly, can I acknowledge that I simply do not know?

Logic, Physics and Ethics

Despite the importance of logic, the later Stoics also warned against becoming overly absorbed in philosophical technicalities.

Epictetus and Marcus Aurelius recognised that the study of argument could become another intellectual pursuit disconnected from the actual practice of philosophy.

The purpose of Stoicism was never simply to produce clever logicians.

It was to cultivate wise human beings.

This is why the Stoics understood logic, physics and ethics as interconnected.

Logic concerns our capacity to reason correctly and examine impressions.

Physics concerns our understanding of Nature, the world we inhabit and our place within it.

Ethics concerns how we ought to live, how we treat others and how we cultivate excellence of character.

Logic alone cannot tell us what is genuinely worth pursuing unless we also have some understanding of the good.

Nor does knowing how to construct a valid argument guarantee that we will act wisely.

The Stoic project requires the integration of understanding, judgement and action.

Perhaps we could say that logic helps us determine whether our judgements are justified, physics helps us understand the reality within which we live, and ethics guides us toward living well within that reality.

Together, they provide the foundations for a philosophical way of life.

Philosophy as a Practice of Attention

One of the most interesting conclusions to emerge from our discussion was that Stoic logic may be understood as a discipline of attention.

We ordinarily move through life accepting impressions almost automatically.

Something happens, we interpret it, and before long we are emotionally and behaviourally committed to a particular understanding of the situation.

The Stoics invite us to interrupt this process.

Not by withdrawing from experience, but by attending more carefully to what experience presents.

We can learn to notice when an impression is being transformed into a judgement, when a judgement rests upon an uncertain premise, and when an apparently reasonable conclusion depends upon a mistaken understanding of what is good.

This is not simply about becoming more intellectually precise.

It is about becoming less easily deceived, less vulnerable to unnecessary disturbance, and increasingly capable of meeting life with wisdom.

And perhaps that is the most important lesson of Stoic logic.

The quality of our lives depends, in no small part, upon the quality of the judgements through which we understand them.

Learning to reason well is therefore not separate from learning to live well.

It is part of the same undertaking.

Brisbane Stoics: Philosophy Among Friends

Our October meeting attracted around 40 participants and generated plenty of lively discussion, demonstrating that even a technical subject such as logic can become an engaging topic when explored cooperatively.

As usual, many members continued their conversations afterwards over coffee at a nearby café.

These gatherings remind us that philosophy need not be a solitary activity. The exchange of ideas, the testing of arguments and the willingness to reconsider our own assumptions are all enriched through conversation with others.

Brisbane Stoics meets at 9:00am on the second Sunday of each month at the New Farm Library meeting room.

Everyone is welcome, regardless of their familiarity with Stoicism. Our aim is to explore philosophy together, not simply as an academic subject, but as a practical way of learning how to live well.