Stoic Criteria for Cognitive Impressions
1. Introduction
Stoicism was a philosophy born in the bloody and turbulent ancient world. Beginning in the Hellenistic period and ending with the Roman empire, its proponents counted people of incredibly different backgrounds, from the slave-born Epictetus and to the Roman emperor Marcus Aurelius, the hobo Zeno to the statesman Seneca. Yet these very different people all sought salvation in this same philosophy. Stoicism was renowned for its incredibly high standards in epistemology and ethics. It seems odd that such a demanding philosophy should thrive, adding to the troubles of the already tough lives of ancient people. But it was this very demandingness that solved their problems. Their salvation was through self-mastery. In the stringent doctrines of Stoicism lie a most hopeful belief, that Nature endows the human spirit with a rationality that can trump all suffering. Man can be tranquil by virtue and knowledge alone, and both are in his power. I don’t know about you, but I’ve got my problems in the modern world too. I may not have the gory special effects, but plenty of things are outside my control. So when they tell me that it is completely up to me to get my peace of mind, I get very curious. Stoic philosophy is holistic and consistent throughout its different branches. Their physics, ethics and logic inform each other and do not make sense without each other. A relevant example is their Socratic belief that virtue is knowledge. Knowledge is the first step to virtue and tranquility. This essay explores the implications of the interdependence between Stoicism’ branches for its epistemology, in particular cognitive impressions.
2. Epistemology
Stoic epistemology aims to prove the possibility of a perfect sage. It doesn’t matter whether such a person has or would ever exist. The point is to establish an ideal and perfect standard of wisdom to strive towards. Such a sage doesn’t need to know everything. He must only be able to distinguish between certainty and doubt. He accepts that which is guaranteed to be true, and suspends judgement in all other cases. Interestingly, this principle of suspending judgement upon uncertainty the Stoics shared with the Sceptics. The difference is that the Sceptics, depending on the specific school, thought that certainty hadn’t yet been achieved or could never be achieved. The task of the Stoics, then, is to show that we can achieve certainty, and distinguish it from mere belief. In the Stoic view, all learning starts with sensory perception.1 These sensory inputs give rise to perceptual impressions. Then, with our memory, we record repeated and similar impressions as an experience. without intention or design, we form ‘common notions’ based on our perceptual experiences.2 Not only are these natural concepts our ‘first principles’, acquired via natural induction, it is also on their basis that the human capacity for Reason matures. With matured Reason and these natural notions as starting points, a person can infer true knowledge and wisdom. For this last step of inference, the Stoics developed their logic. Tracing backwards the chain of learning, we see that knowledge (or the possibility thereof) is based on impressions. We can say: the Impression is the basic building block of knowledge. The quality of the blocks make up the quality of the whole. So to guarantee the truth of the acquired ‘natural’ concepts, we must guarantee the truth of the impressions the concepts are built on.
Here, it is relevant to point out that the Stoics distinguish between sensory inputs and sensory impressions. According to them, all impressions are made in and by the mind.3 In more modern terms, we can say that the sensory input is the raw signal pre-mind-processing, and that the sensory impression is a mental representation of the sensory input. The premise that all impressions are formed in and by the mind has important implications for the intermediary steps between sensory input and knowledge. The Stoic conception of the mind, the ‘leading part of the soul’, is strongly monistic. Even though the human soul has many abilities, these abilities are all parts of one singular commanding faculty, the mind.4 For example, sight resides in the part of the mind reserved for sight.
How does the impression fit into their monistic conception of mind? Zeno defined it as “an imprinting in the soul”5. The Stoics’ first interpretation of this was a physical imprinting like a stamp on warm wax. Chrysippus thought this ridiculous, since we can have many impressions of different things simultaneously, but that physical things could not have different shapes simultaneously. He interpreted ‘imprinting’ as an alteration in the soul. The later Stoics added that the alteration must be in the relevant part of the soul only, that is the ‘leading’ part (the mind). Their last amendment was that the alteration must be passive and not active, since impressions are ways of being affected and not an activity. They come about from the impact of external things or from effects in us, they said. The final version thus defines impressions as passive alterations in the mind.
The last amendment means that impressions are involuntary. This is curious, considering impressions are formed in and by the mind, the ‘commander’ of the soul. That very same commanding faculty possesses another power, the Stoics claim: the power of ‘assent’. We cannot choose the appearance of impressions, but we can choose whether we assent to the impression or not, that is, whether we accept them as true or not. Not to assent is to suspend judgement. Since impressions and assent are both faculties of the same mind, our will is always unified. Thus, in the Stoic view, there is no such thing as conflict between the irrational and rational parts of us, since they are part of the same commanding faculty. So if our reason is disciplined enough, we are capable of always doing the right thing. In ethics this means that we always can always choose to be virtuous. In epistemology, we can always choose to suspend judgement under uncertainty, thereby never making mistakes. With this rationale, the Stoics formalized a 4-step program for learning and acquiring true knowledge: (1) Sensory Perception (2) Discerning whether impressions are true or false (3) Assenting only to true impressions and (4) Deducing from these accepted true impressions further principles using correct inference (Stoic logic).
3. Ontology
Aëtius says that our mind starts out as a blank slate, and the first pieces of information we get are sensory. For the Stoics, however, not only is sensory information the beginning of knowledge, it is the foundation of knowledge. To understand why sensory impressions are fundamental in their epistemology, we need to understand their ontology. According to them, for something to have being (enei), or existence, it must have the capacity to act or be acted upon. To this criterion they add that only bodies can cause anything (act) or be acted upon. Therefore, only bodies exist. Matter is the body which can be acted upon, the passive principle. Logos is the body which acts, the active principle. The Logos is the Stoic Providence that is present in and fused with all matter. It acts on matter in an rational, intelligent, orderly manner, according to its divine plan. All being is a living unity between matter and logos, the passive and active principle, and the two are inseparable. Body and soul as a living whole is a good analogy for the Stoic cosmos. The soul (logos) is the source of life, movement, structure, action, and it is present and acts throughout the body (matter). The important takeaway is this: Being includes anything that can affect or be affected. Only bodies can affect or be affected (hence, even the soul, the mind, virtue and wisdom are bodies). Nothing incorporeal exists.
But existing things do not exhaust their ontology. The Stoics identify another class of things that do not exist, yet are not nothing either.6 They subsist (huphistanei). They are incorporeal, which is why they do not exist, but they are not nothing because they are crucial to understanding existent things, even for making them possible.7 Bodies need ‘somewhere’ to exist, so space subsists. For bodies to affect each other, time is necessary for the ‘before’ and ‘after’ of their causal chains. The most important subsistent thing for our inquiry is the sayable (lekton). A sayable can be roughly defined as something that can be said. They relate to existent things by being what can be said about them, and are crucial to our explanations of the physical world. The notion of sayable is used across Stoic ontology, epistemology, logic and philosophy of language. This gives a first glimpse into how related and interdependent the different branches of philosophy are in Stoicism. In philosophy of language, a sayable can be the meaning of what is said. In ontology, it can be the incorporeal substance for the content of thoughts. It is important to understand that while sayable do not ‘exist’ (enei), they are part of the inventory of the world as incorporeal, metaphysical items. They are ‘out there’, independent of whether we think of them, say them, agree with them or not. Much like facts exist, whether we discover them or not (indeed, facts are a special kind of sayable). Sayables are basically everything that could possibly be said.
There are many kinds of sayables, claims or propositions being the most important kind for Stoicism, and for our inquiry in particular. A complete propositional sayable consists of a subject8 and a predicate,9 equivalent to ‘simple assertions’ in Stoic logic. They are ‘complete’ because they can be true or false, and they transfer seamlessly to logic. By contrast, predicates or subjects alone cannot be true or false, and are incomplete sayable. As examples of simple assertions in their logic, the Stoics often used claims like ‘It is day.’ The truth value of such assertions cannot be deduced, but only verified through sensory perception, to check whether the propositional content corresponds to the state of the physical world. This correspondence-theory attests to how inseparable their logic and physics are. Further evidence for this inseparability is that the predicate plays an essential role in Stoic causality. Keep in mind that the predicate is both an incorporeal subcomponent of a sayable, in the ontological domain, and the part of a proposition that says something about the subject, in the logical domain. In the Stoic account of causality, both the cause and the receiver of the effect are bodies, but the effect itself is a predicate. For example: Wisdom caused Socrates to ‘be wise’. Wisdom is the body that causes, Socrates is the body that receives the effect, and the incorporeal predicate ‘being wise’ is the effect itself. So causal chains between bodies cannot be explained without incorporeals, which are the effects. In this way, incorporeals aren’t any less important, nor any less ‘real’, than physical things.10
Given their ontology and causality, the Stoics understood impressions as having a literal physical realization. For a soul to ‘get an impression’ (an incorporeal predicate), the effect must have been caused by a body, or multiple bodies. Remember that impressions are passive mind alterations coming from the impact of either external things or from effects in us. Thus, the bodies causing impressions must be external or internal bodies. Specifically sensory impressions are the effect of external bodies on our minds. So it makes sense that sense perceptions should serve as our foundation for knowledge, since it is through them that we have contact with existent things. Nature, in all its divine wisdom, has given us “the sensory capacity, and impression, which comes about by means of it, as a sort of light for the recognition of the truth.”11 But while sensory impressions are their starting point for knowledge, the Stoics did not believe all sensations to be true. Sensations alone are not their criterion of truth. A criterion of truth is an instrument for determining that something is true with absolute certainty.12 To qualify as a criterion of truth for the stringent Stoics, the impression in question must be guaranteed to be true. They call this privileged type of impression a ‘cognitive impression’ (phantasia katalêptikê).13 The question is, what guarantees the truth of this ‘cognitive impression’? What distinguishes it from other types of impressions?
4. Cognitive Impressions
A look at their classification of impressions should enlighten us. They start by dividing impressions into persuasive and unpersuasive ones. Being creatures with perception, the persuasiveness of the sensory impression must have something to do with how closely it resembles our prior experiences of the material world. Sextus gives an example very typical of Stoic logic: “If it is dark, it is day”14 would be unpersuasive. Of persuasive impressions some are true, some false, some both, and some neither. True impressions are those of which one can make true predications. Sextus illustrates the distinction between true and false impressions with Orestes’ hallucination is particularly enlightening:
“in so far as it [his impression] struck him as from some real thing it was true (for Electra was real), but in so far as it struck him as from a Fury it was false (for there was no Fury)“15
Orestes’ impression was true in the sense that it came about from a real thing, but it was false because it didn’t represent that same real thing. These two ways in which an impression can be true or false give rise to the first and second criteria for cognitive impressions.
First and second criteria
To be true and cognitive, the impression has to
(1) come about from what is , and
(2) be formed in exact accordance with (that same) what is 16
‘What is’ in the original Greek can refer either to an existent thing (enei) or a fact (hyparchein).17 So how these two criteria are to be met depends on the nature of the source of the impression, that is, whether this ‘what is’ is an existent thing or a fact. In cases where it is an existent thing, understanding these two criteria is a straightforward matter thanks to Stoic physics. Only bodies exist, therefore, the first criterion is met if the source of the impression is a physical object. This is the case with all sensory perceptions, as we saw in the Ontology section, and by contrast, hallucinations do not meet this first criterion. The second criterion is met if the impression represents that same object faithfully. Orestes is an example where the first criteria is met but the second is not, since the object in his impression doesn’t correspond to physical reality. It is possible that the Stoics take the meaning ‘what exists’ when talking about children specifically. They saw children as irrational beings without minds and incapable of registering facts. However, irrational beings could still have cognitive impressions via faithful sensory perception of physical objects. This ties back to sensory perceptions being the starting point of learning, leading to the common notions that develop rationality and act as first principles.
Adults, by contrast, are rational beings. Formed in and by the mind, all our impressions are thoughts. We turn even our perceptive impressions into propositional content.18 For example, seeing a green object, our impression would include the concept ‘green’. Here, Stoic epistemology ties back to ontology and logic: The mind and its mental states, including impressions, are physical bodies. But the contents of impressions and thoughts are incorporeal sayables. So for our impressions to be true, the sayables in our impressions have to be true. Stoics gave true sayables an upgraded ontological status. Rather than merely subsisting, they are ‘present’ (hyparchon) in the world as facts, which is the second meaning of ‘what is’.
So in the second meaning, cognitive impressions must come about from true sayables, and be in exact accordance with them. Note that ‘come about from’ doesn’t have to mean ‘caused by’, which requires the cause be a body, which a true sayable is not. In the Stoic view, facts can indeed move us to form impressions, despite being incorporeal.19 How the truth value of propositional sayables can be evaluated, we saw in our treatment of simple assertions in logic: They are true if they correspond to physical reality. How does this correspondence proceed exactly? To find out, we need to examine the nature of the ‘presence’ of true sayables.20 According to the Stoics, if a sayable is true, it exists metaphysically in the world, and it does so in the form of a fact. And it isn’t only at the level of complete sayables the hyparchein status is given. The subcomponents of a true sayable are ‘present’ as well. If true, the predicate exists metaphysically in the world as an attribute to the subject. Predicates, like complete sayables, are always incorporeal no matter their truth value. By contrast, the subject in a true sayable is not only ‘present’, but also exists physically in the world. For example, if ‘Cato is walking’ is true, then Cato is a physical man that exists.
The connection between these subcomponents and their ontological counterparts directly impacts the truth value of the sayable as a complete assertion. If just one of either the subject or the attribute to that same subject aren’t present in the world, then the sayable as a whole is false. And if the sayable as a whole is false, then it cannot serve as ‘what is’ in the first and second criteria for cognitive impressions. In summary, for an adult’s impression to come about from, and be in accordance with, a fact means that the propositional content of his impression has to be true. And this is the case when his thought-sayables and their parts correspond with physical reality. In the end, despite adults differing from children in forming rational impressions, Stoic logic and physics are so inseparable that the adults must refer to the physical world as often as the children, just perhaps in a more multistep manner.
Third criterion
The Stoics, however, are still not satisfied. It is not enough for them that the propositional content of the impression be true.21 Of true impressions (those that meet the first two criteria), some are cognitive and some are not.22 The impression must be guaranteed to be true to be called cognitive.
How is it possible to have a true impression that doesn’t guarantee truth? The third and final criterion for cognitive impressions points the way:
(3) that it be such that it could not come about from what is not.23
This third criterion, rather than being an additional feature of cognitive impressions, elaborates on the first two criteria.24 It reinforces the first criterion by emphasizing that the impression cannot come from what is not an existing object. In other words, it must not be a hallucination. Further, the truth has to feel certain to the one observing it. People who suffer hallucinations cannot trust that any given impression of theirs is true. Their true and false impressions are equally persuasive, so the true ones have no distinctiveness and recognizability. Their impressions can therefore never be cognitive, since they do not guarantee truth.
For the second criterion, the third criterion acts as an extension: The cognitive impression is in exact accordance with what is, so exact such that it cannot come about from what is not. This means that the impression must represent the thing (or the fact) so accurately, in all the necessary detail, such that it cannot possibly be confused with something else, particularly the things most similar to it. To be successful in this, (1) the impression must include all the relevant and distinctive features of the thing and (2) these features themselves must be represented distinctively, that is, accurately and in sufficient detail. In short, all distinctive features are distinctively represented.
The Sceptics heavily objected to the third criterion.25 They denied that impressions existed, that could never confuse one thing with another, because some things are so similar that they are practically indiscernible. But in light of Stoic physics being so materialistic, if two things are indistinguishable, they are the same thing. So the impression would be true in representing two indiscernibles as the same thing. In uncertain cases where the things can indeed be discerned, but it is very hard to do so, the perfect sage would know to suspend judgement. One mustn't be epistemologically overwhelmed by the Stoic sage. It is an ideal, and the Stoics encourage and approve of any effort made towards improving one’s discernment. If we reduce our ambition, we can easily imagine how we can get closer to this ideal. In perceptive cases where an impression is blurry and indistinct, uncertainty and error can be reduced simply by getting closer for better detail. Factual impressions are more complicated to discern, however. Verification of these requires a combination of logic, sensory perception, ontology, even ethics. It was beyond the scope of this essay to explore how ethics informs our judgement. But given how holistic Stoicism is, as we have seen, any or all of its branches might be involved in judging a given impression’s cognitivity.
5. Conclusion
In summary, an impression that meets the three aforementioned criteria is cognitive. The mode of assessing whether these criteria are met depends on whether the source of the impression is a physical object or a fact. In assenting to a cognitive impression, we have a piece of true knowledge. Our perceptual cognitive impressions are the basis of our first principles. From these can be inferred true knowledge by proper methods of inference. This involves all branches of Stoic philosophy, so to improve our discernment and get closer to the ideal of the sage, the Stoics would recommend we study all the branches of Stoic philosophy. The sage is someone who, starting with zero knowledge, makes a continuous and conscious effort to repeatedly distinguish between cognitive and non-cognitive impressions. He assents to cognitive impressions and always suspends judgement whenever there is uncertainty. In this way, he increases his collection of true pieces of information. Upon reaching a large enough collection of cognitive impressions, he forms natural concepts and his rationality matures. He makes connections between these concepts and applies logic to infer further truths from them. Continuing this process, at some point, he attains knowledge and wisdom, and is directly rewarded with virtue and tranquility.
Reference List
Baltzly, D., (2019). ‘Stoicism’, The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.), <https://plato.stanford.edu/archives/spr2019/entries/stoicism/>.
Bobzein, S., (1996). ‘Stoic Syllogistic’, Oxford Studies in Ancient Philosophy, 14
Boeri, M. D. (2001). ‘The Stoics on Bodies and Incorporeals’. The Review of Metaphysics, 54(4), 723–752. <http://www.jstor.org/stable/20131617>.
Frede, M., 'Stoic Epistemology', in Algra, K., Barnes, J., Mansfeld, J., & Schofield, M. (Eds.). (1999). The Cambridge History of Hellenistic Philosophy. Cambridge: Cambridge University Press, 295-322
Frede, M., ‘The Stoic Notion of a Lekton’, in S. Everson, (1994). Language. Cambridge, 109–128.
Primary texts
Aëtius, Placita iv.11
Diogenes Laertios, vii.45-46
Sextus Empiricus, Adv. math. vii.227-260
Aëtius, Placita iv.11↩︎
Frede 2008↩︎
Frede 2008↩︎
Baltzly 2019↩︎
Sextus M vii. 228↩︎
Frede 1994↩︎
Boeri 2001↩︎
Frede 1994. Note: I replaced Frede’s ‘case’ with ‘subject’, because the notion of a case as an immanent Form is beyond the scope of this essay. For our purpose of equating the propositional sayables with simple assertions in logic, ‘subject’ will suffice.↩︎
Bobzein 1996↩︎
Boeri 2001↩︎
Sextus M vii.259↩︎
Baltzly 2019↩︎
In this context, the Stoics do not mean ‘cognitive’ in the sense of mental activity. They meant it in the sense of ‘an impression that firmly grasps its object’ in the original Greek (Baltzly 2019).↩︎
Sextus M vii.243↩︎
Sextus M.vii.245, emphasis added↩︎
D.L. vii.46; Sextus M xi.183; cf. Cicero Acad. ii.77; Frede 2008↩︎
Frede 2008↩︎
Frede 1994↩︎
Frede 2008↩︎
Frede 1994↩︎
Frede 2008, 304↩︎
Sextus M vii.247↩︎
Sextus M vii.248↩︎
Frede 2008↩︎
Baltzly 2019↩︎