Impression, Assent, Cognitive Impression, Cognition, Knowledge
The writings of the early Stoics (Zeno, Cleanthes, and Chrysippus) have been almost completely lost. What is known about these philosophers depends on subsequent writers.
We know from Cicero that Zeno made some "new pronouncement" in epistemology and that these pronouncements used some new terminology, which Cicero tries to translate.
Cicero (106 - 43 BCE)
"[The Stoics] assert that there are three criteria—knowledge (ἐπιστήμην) and opinion (δόξαν) and, set midway between
these two, cognition (κατάληψιν); and of these knowledge is the unerring and firm cognition which is
unalterable by reason, and opinion is weak and false assent, and apprehension is intermediate between
these, being assent to a cognitive impression (καταληπτικῆς φαντασίας); and a cognitive impression, according to
them, is one which is true and of such a kind as to be incapable of becoming false. And they say that,
of these, knowledge subsists only in the wise, and opinion only in the fools, but cognition is
shared alike by both, and it is the criterion of truth"
(Sextus Empricius, Against the Logicians I.151-153).
"These men [the Stoics], then, assert that the criterion of truth is the cognitive impression" (Sextus Empiricus, Against the Logicians I.227).
"[A cognitive impression] being plainly evident and striking, lays hold of us, almost by the very hair, as they say, and drags us off to assent (συγκατάθεσιν), needing nothing else to help it to be thus impressive or to suggest its superiority over all others. For this reason, too, every man, when he is anxious to cognize any object exactly, appears of himself to pursue after an impression of this kind—as, for instance, in the case of visible things, when he receives a dim impression of the real object. For he intensifies his gaze and draws close to the object of sight so as not to go wholly astray, and rubs his eyes and in general uses every means until he can receive a clear and striking impression of the thing under inspection, as though he considered that the credibility of the cognition (τὴν τῆς καταλήψεως πίστιν) depended upon that" (Sextus Empiricus, Against the Logicians I.257-258).
"[A]ccording to the Stoics the cognitive impression is judged to be cognitive by the fact that it proceeds from an existing object and in such a way as to bear the impress and stamp of that existing object; and the existing object is approved as existent because of its exciting a cognitive impression" (Sextus Empiricus, Against the Ethicists 183).
"When a man is born, the Stoics say, he has the commanding-part of his soul (τὸ ἡγεμονικὸν μέρος τῆς ψυχῆς) like a sheet of paper ready for writing upon. On this he inscribes each of his conceptions (ἐννοιῶν). The first method of inscription is through the senses. For by perceiving something, e.g., white, they have a memory of it when it has departed. And when many memories of a similar kind have occurred, we then say we have experience (ἐμπειρίαν). For the plurality of similar impressions is experience. Some conceptions arise naturally in the aforesaid ways and undesignatedly, others through our own instruction and attention. The later are called 'conceptions (ἔννοιαι)' only, the former are called 'preconceptions (προλήψεων)' as well. Reason (λόγος), for which we are called rational (λογικοί), is said to be completed from our preconceptions (προλήψεων) during our first seven years" (Pseudo-Plutarch, Placita 4.11).
Pseudo-Plutarch (2nd century CE) Placita Philosophorum (Views of the Philosophers) (once wrongly attributed to Plutarch) sets out five books of views of the philosophers on physics. Stobaeus (5th century CE) and Theodoret (5th century CE) preserve parts of this same work. Theodoret names (the otherwise unknown) Aëtius as the source. (The tradition of works of the views of the philosophers on physics begins with Theophrastus, Aristotle's successor in the Lyceum. Diogenes Laertius lists "sixteen books of Physical Opinions" in the catalog of works he attributes to Theophrastus (Lives of the Philosophers V.2.48).)
"Now the part which deals with canons or criteria they admit as a means for the discovery of truth, since in the course of it they explain the different kinds of impressions that we have. And similarly the part about definitions is accepted as a means of recognizing truth, inasmuch as things are apprehended by means of general notions (ἐννοιῶν)" (Diogenes Laertius, Lives of the Philosophers VII.1.42).
"An impression is an imprint on the soul: the name having been appropriately borrowed from the imprint made by the seal upon the wax. Of impressions, some are cognitive and some are not-cognitive. The former, which they say is the criterion of reality, is defined as that which proceeds from a real object, agrees with that object itself, and has been imprinted seal-fashion and stamped upon the mind: the latter, or non-cognitive, that which does not proceed from any real object, or, if it does, fails to agree with the reality itself, not being clear or distinct (μὴ τρανῆ μηδὲ ἔκτυπον)" (Diogenes Laertius, Lives of the Philosophers VII.1.45-46).
"Irrefutability is strength in argument so as not to be brought over by it to the opposite side. Earnestness is a habit of referring impressions to right reason. Knowledge itself they define either as secure cognition or as a habit or state which in reception of impressions cannot be shaken by argument. Without the study of dialectic (διαλεκτικῆς), they say, the wise man cannot guard himself in argument so as never to fall; for it enables him to distinguish between truth and falsehood, and to discriminate what is merely plausible and what is ambiguously expressed, and without it he cannot methodically put questions and give answers" (Diogenes Laertius, Lives of the Philosophers VII.1.47).
"The Stoics agree to put in the forefront the doctrine of impression and sensation, inasmuch as the criterion by which the truth of things is tested is generically an impression, and again the theory of assent (συγκαταθέσεως) and that of cognition (καταλήψεως) and thought (νοήσεως), which precedes all the rest, cannot be stated apart from impression. For impression comes first; then thought, which is capable of expressing itself, puts into the form of a proposition that which the subject receives from an impression" (Diogenes Laertius, Lives of the Philosophers VII.1.49).
"The criterion of truth they declare to be the cognitive impression, i.e. that which comes from a real object--according to Chrysippus in the twelfth book of his Physics.... In the first book of his Exposition of Doctrine, he contradicts himself and declares that sensation and preconception (αἴσθησιν καὶ πρόληψιν) are the only standards, preconception being a general notion (ἔννοια) which comes by the gift of nature" (Diogenes Laertius, Lives of the Philosophers VII.1.54). "Here first of all he [Zeno of Citium, founder of the Stoic school] made some new pronouncements about sensation itself [about the faculty of the senses, that in terms of which animals and human beings situate themselves in the world], which he held to be [a faculty in which there is] a combination of a sort of impact offered from outside (which he called [in Greek] φαντασίαν and we may call an impression, and let us retain this term at all events, for we shall have to employ it several times in the remainder of my discourse),—well, to these impressions received by the senses he joins the act of mental assent [or: assent of our minds] which he makes out to reside within us and to be a voluntary act. He held that not all impressions are trustworthy [and hence worthy of assent] but only those that have a 'manifestation,' peculiar to themselves, of the objects presented; and a trustworthy impression [cognitive impression], being perceived as such by its own intrinsic nature, he termed ‘graspable’[an impression to which assent results in a cognition]—will you endure these coinages?
Indeed we will, for how else could you express καταληπτόν [which in Greek means "capable of being seized, apprehended, or grasped"]?
But after it [the cognitive impression] had been received and accepted as true, he termed it a 'grasp' [a 'cognition'] resembling objects gripped in the hand—and in fact he had derived the actual term from manual prehension, nobody before having used the word in such a sense, and he also used a number of new terms (for his doctrines were new). Well, a thing grasped by the senses he called itself a sensation, and a sensation so firmly grasped as to be irremovable by reasoning he termed knowledge, but a sensation not so grasped he termed ignorance, and this was the source also of opinion, an unstable impression akin to falsehood and ignorance. But as a stage between knowledge and ignorance he placed that ‘grasp’ of which I have spoken.... On the strength of this he deemed the senses also trustworthy, because, as I said above, he held that a grasp achieved by the senses was both true and trustworthy, not because it grasped all the properties of the thing, but because it let go nothing that was capable of being its object, and because nature had bestowed as it were a 'measuring-rod' of knowledge and a first principle of itself from which subsequently notions of things could be impressed upon the mind, out of which not first principles only but certain broader roads to the discovery of reasoned truth were opened up. On the other hand error, rashness, ignorance, opinion, suspicion, and in a word all the things alien to firm and steady assent, Zeno set apart from virtue and wisdom. And it is on these points more or less that all Zeno’s departure and disagreement from the doctrine of his predecessors turned" (Academica I.40-42).
"Next [in the process that results in reason in human beings] follows the rest of the series linking on a chain of larger percepts, for instance the following, which embrace as it were a fully completed grasp of the objects: 'If it is a human being, it is a rational mortal animal.' From this class of percept are imprinted upon us our notions of things, without which all understanding and all investigation and discussion are impossible. But if false notions existed (I understood you to employ 'notions' to render [the Greek] ἐννοίας [which in Greek means "notion or conception"]—well, if there were these false notions or notions imprinted on the mind by impressions of a kind that could not be distinguished from false ones, how pray could we act on them? how moreover could we see what is consistent with any given fact and what inconsistent" (Academica II.21-22)?
"[T]here must be a first principle established for wisdom to follow when she embarks on any action, and this first principle must be consistent with nature; for otherwise appetition (our chosen equivalent for the term ὁρμήν [which in Greek means "impulse"]), by which we are impelled to action and seek to get an object presented to our vision, cannot be set in motion; but the thing that sets it in motion must first of all be seen, and must be believed in, which cannot take place if an object seen will be indistinguishable from a false one; but how can the mind be moved to appetition if it does not perceive whether the object seen is consistent with nature or foreign to it? And moreover if it has not struck the mind what its function is, it will never do anything at all, never be driven towards any object, never make a movement; whereas if it is at some time to do something, what strikes it must seem to it to be true" (Academica II.24-25).
"[T]he amount of craftsmanship that nature has employed in the construction first of every animal, then most of all in man,—the power possessed by the senses, the way in which we are first struck by the sense-presentations, next follows appetition imparted by their impact, and then we direct the senses to perceive the objects. For the mind itself, which is the source of the sensations and even is itself sensation, has a natural force which it directs to the things by which it is moved. Accordingly some sense-presentations it seizes on so as to make use of them at once, others it as it were stores away, these being the source of memory, while all the rest it unites into systems by their mutual resemblances, and from these are formed the concepts of objects which the Greeks term sometimes ἐννοίας and sometimes προλήψεις. When thereto there has been added reason and logical proof and an innumerable multitude of facts, then comes the clear perception of all these things, and also this same reason having been by these stages made complete finally attains to wisdom. Since therefore the mind of man is supremely well adapted for the knowledge of things and for consistency of life, it embraces information very readily, and your κατάληψιν, which as I said we will express by a literal translation as ‘grasp,’ is loved by the mind both for itself (for nothing is dearer to the mind than the light of truth) and also for the sake of its utility. Hence the mind employs the senses, and also creates the sciences as a second set of senses, and strengthens the structure of philosophy itself to the point where it may produce virtue, the sole source of the ordering of the whole of life" (Academica II.30-31).
"[L]et us say a few words on the subject of ‘assent’ or approval (termed in Greek συγκατάθεσιν)—not that it is not a wide topic, but the foundations have been laid a little time back. For while we were explaining the power residing in the senses, it was at the same time disclosed that many things are grasped and perceived by the senses, which cannot happen without the act of assent" (Academica II.37).
"[T]he mind must necessarily yield to clear impressions: since just as no animal can refrain from seeking to get a thing that is presented to its view as suited to its nature (the Greeks term it οἰκεῖον), so the mind cannot refrain from giving approval to a clear object when presented to it" (Academica II.38).
"Zeno used to demonstrate by gesture: for he would display his hand in front of one with the fingers stretched out and say 'An impression is like this'; next he closed his fingers a little and said, 'An act of assent is like this'; then he pressed his fingers closely together and made a fist, and said that that was comprehension [cognition] (and from this illustration he gave to that process the actual name of κατάληψιν, which it had not had before); but then he used to apply his left hand to his right fist and squeeze it tightly and forcibly, and then say that such was knowledge, which was within the power of nobody save the wise man—but who is a wise man or ever has been even they themselves do not usually say" (Academica II.145).