Epistemology
Epicurean epistemology has three criteria of truth: sensations (aisthêsis), preconceptions (prolepsis), and feelings (pathê). Prolepsis is sometimes translated as "basic grasp" but could also be described as "universal ideas": concepts that are understood by all. An example of prolepsis is the word "man" because every person has a preconceived notion of what a man is. Sensations or sense perception is knowledge that is received from the senses alone. Much like modern science, epicurean philosophy posits that empiricism can be used to sort truth from falsehood. Feelings are more related to ethics than Epicurean physical theory. Feelings merely tell the individual what brings about pleasure and what brings about pain. This is important for the Epicurean because these are the basis for the entire Epicurean ethical doctrine.
According to Epicurus, the basic means for our understanding of things are the 'sensations' (aestheses), 'concepts' (prolepsis), 'emotions' (pathe) and the 'focusing of thought into an impression' (phantastikes epiboles tes dianoias).
Epicureans reject dialectic as confusing (parelkousa) because for the physical philosophers it is sufficient to use the correct words which refer to the concepts of the world. Epicurus then, in his work On the Canon, says that the criteria of truth are the senses, the preconceptions and the feelings. Epicureans add to these the focusing of thought into an impression. He himself is referring to those in his Epitome to Herodotus and in Principal Doctrines.
The senses are the first criterion of truth, since they create the first impressions and testify the existence of the external world. Sensory input is neither subjective nor deceitful, but the misunderstanding comes when the mind adds to or subtracts something from these impressions through our preconceived notions. Therefore, our sensory input alone cannot lead us to inaccuracy, only the concepts and opinions that come from our interpretations of our sensory input can. Therefore our sensory data is the only truly accurate thing which we have to rely for our understanding of the world around us.
And whatever image we receive by direct understanding by our mind or through our sensory organs of the shape or the essential properties that are the true form of the solid object, since it is created by the constant repetition of the image or the impression it has left behind. There is always inaccuracy and error involved in bringing into a judgment an element that is additional to sensory impressions, either to confirm or deny it. — Epicurus said that all the tangible things are real and each impression comes from existing objects and is determined by the object that causes the sensations. — Therefore all the impressions are real, while the preconceived notions are not real and can be modified. If you battle with all your sensations, you will be unable to form a standard for judging which of them are incorrect. —The concepts are the categories which have formed mentally according to our sensory input, for example the concepts "man", "warm", and "sweet", etc. These concepts are directly related to memory and can be recalled at any time, only by the use of the respective word. (Compare the anthropological Sapir–Whorf hypothesis). Epicurus also calls them "the meanings that underlie the words" (hypotetagmena tois phthongois: semantic substance of the words) in his letter to Herodotus. The feelings or emotions (pathe) are related to the senses and the concepts. They are the inner impulses that make us feel like or dislike about certain external objects, which we perceive through the senses, and are associated with the preconceptions that are recalled.
In this moment that the word "man" is spoken, immediately due to the concept an image is projected in the mind which is related to the sensory input data. — First of all Herodotus, we must understand the meanings that underlie the words, so that by referring to them, we may be able to reach judgments about our opinions, matters of inquiry, or problems and leave everything undecided as we can argue endlessly or use words that have no clearly defined meaning. —Apart from these there is the assumption (hypolepsis), which is either the hypothesis or the opinion about something (matter or action), and which can be correct or incorrect. The assumptions are created by our sensations, concepts and emotions. Since they are produced automatically without any rational analysis and verification (see the modern idea of the subconscious) of whether they are correct or not, they need to be confirmed (epimarteresis: confirmation), a process which must follow each assumption.
For beliefs they use the word hypolepsis which they claim can be correct or incorrect. —Referring to the "focusing of thought into an impression" or else "intuitive understandings of the mind", they are the impressions made on the mind that come from our sensations, concepts and emotions and form the basis of our assumptions and beliefs. All this unity (sensation – concept or category – emotion – focusing of thought into an impression) leads to the formation of a certain assumption or belief (hypolepsis). (Compare the modern anthropological concept of a "world view".) Following the lead of Aristotle, Epicurus also refers to impressions in the form of mental images which are projected on the mind. The "correct use of impressions" was something adopted later by the Stoics.
Our assumptions and beliefs have to be 'confirmed', which actually proves if our opinions are either accurate or inaccurate. This verification and confirmation (epimarteresis) can only be done by means of the "evident reason" (henargeia), which means what is self-evident and obvious through our sensory input.
An example is when we see somebody approaching us, first through the sense of eyesight, we perceive that an object is coming closer to us, then through our preconceptions we understand that it is a human being, afterwards through that assumption we can recognize that he is someone we know, for example Theaetetus. This assumption is associated with pleasant or unpleasant emotions accompanied by the respective mental images and impressions (the focusing of our thoughts into an impression), which are related to our feelings toward each other. When he gets close to us, we can confirm (verify) that he is Socrates and not Theaetetus through the proof of our eyesight. Therefore, we have to use the same method to understand everything, even things which are not observable and obvious (adela, imperceptible), that is to say the confirmation through the evident reason (henargeia). In the same way we have to reduce (reductionism) each assumption and belief to something that can be proved through the self-evident reason (empirically verified). Verification theory and reductionism have been adopted, as we know, by the modern philosophy of science. In this way, one can get rid of the incorrect assumptions and beliefs (biases) and finally settle on the real (confirmed) facts.
Consequently the confirmation and lack of disagreement is the criterion of accuracy of something, while non-confirmation and disagreement is the criterion of its inaccuracy. The basis and foundation of everything are the obvious and self-evident . —All the above mentioned criteria of knowledge form the basic principles of the method, that Epicurus followed in order to find the truth. He described this method in his work On the Canon or On the Criteria.
If you reject any sensation and you do not distinguish between the opinion based on what awaits confirmation and evidence already available based on the senses, the feelings and every intuitive faculty of the mind, you will send the remaining sensations into a turmoil with your foolish opinions, thus getting rid of every standard for judging. And if among the perceptions based on beliefs are things that are verified and things that are not, you are guaranteed to be in error since you have kept everything that leads to uncertainty concerning the correct and incorrect. —(Based on excerpt from Epicurus' Gnoseology 'Handbook of Greek Philosophy: From Thales to the Stoics Analysis and Fragments', Nikolaos Bakalis, Trafford Publishing 2005, ISBN 1-4120-4843-5)
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