Question: What word is both the name of Euphronius of the Athenian dem Sunium's son and is also one of Plato's diaglogues concerning the nature of knowledge?

<P0-S0> The Theaetetus ( ; Greek: Θεαίτητος ) is one of Plato's dialogues concerning the nature of knowledge, written "circa" 369 BC. <SEP> <P1-S0> Theaetetus of Athens ( ; Greek: Θεαίτητος ; c. 417 – 368 BC), possibly the son of Euphronius of the Athenian deme Sunium, was a Greek mathematician. <P1-S1>  His principal contributions were on irrational lengths, which was included in "Book X" of Euclid's "Elements", and proving that there are precisely five regular convex polyhedra. <P1-S2>  A friend of Socrates and Plato, he is the central character in Plato's eponymous Socratic dialogue. <SEP> <P2-S0>  Dei x): The visible sacrifice is the sacrament. <P2-S1>  It does not matter that the minister of the sacraments may be a sinner, or evil. <P2-S2>  It is a part of human nature to acquire knowledge of the intelligible from the sensible. <P2-S3>  Augustine (commenting on John 1,33): "He upon Whom you shall see the Spirit, ...that John did not know that our Lord, having the authority of baptizing, would keep it to Himself, but that the ministry would certainly pass to both good and evil men...What is a bad minister to you, wherever the Lord is good?" <P2-S4>  It is necessary for salvation that humans united together in the name of true religion. <P2-S5>  A sign is the way one obtains knowledge of something else. <P2-S6>  Furthermore, the effects of the sacraments is justification. <P2-S7>  Therefore, it is proper that the remedy have a corporeal side, leading to the spiritual. <P2-S8>  Ephesians 5, 25-26: "Christ loved the Church, and delivered Himself up for it; that He might sanctify it, cleansing it by the laver of water in the word of life." <P2-S9>  It can be found through his writings in the "Summa contra Gentiles" and in the "Summa Theologiæ". <P2-S10>  This is the sacred sign of the invisible sacrifice. <P2-S11>  Therefore, sacraments are necessary for man's salvation. <P2-S12>  Divine Wisdom provides for each thing according to its mode. <P2-S13>  Augustine (Contra Faust xix): "It is impossible to keep men together in one religious denomination, whether true or false, except they be united by means of visible signs or sacraments." <P2-S14>  St. Augustine says (De Civ. <SEP> <P3-S0> The analogy of the sun (or simile of the sun or metaphor of the sun) is found in the sixth book of "The Republic" (507b–509c), written by the Greek philosopher Plato as a dialogue between Glaucon (Plato's elder brother) and Socrates (narrated by the latter). <P3-S1>  Upon being urged by Glaucon to define goodness, a cautious Socrates professes himself incapable of doing so. <P3-S2>  Instead he draws an analogy and offers to talk about "the child of goodness" (Greek: "ἔκγονός τε τοῦ ἀγαθοῦ" ). <P3-S3>  Socrates reveals this "child of goodness" to be the sun, proposing that just as the sun illuminates, bestowing the ability to see and be seen by the eye, with its light so the idea of goodness illumines the intelligible with truth. <P3-S4>  While the analogy sets forth both epistemological and ontological theories, it is debated whether these are most authentic to the teaching of Socrates or its later interpretations by Plato. <P3-S5>  The sun is a metaphor for the nature of reality and knowledge concerning it.