希波克拉底
希波克拉底塑像及誓詞他認為，人類正如宇宙中的其他部分一樣，是由四種元素——土、氣、水、火組成的，這四種元素和人體中的四種液體（黑膽汁、黃膽汁、血液和粘液）相對應。這四種液體處於平衡時，人就是健康的；失衡時，人就會得病。這種理論幾乎一直延續到19世紀。
希波克拉底誓詞意義
希波克拉底最為讓人紀念的是不是上述醫學，而是他留下的《希波克拉底誓言》。這個誓言總共只有五百多個字（按中文計），但是產生的影響卻非常深遠。幾乎所有學醫學的學生，入學的第一課就要學《希波克拉底誓言》，而且要求正式宣誓，可以說醫學界的人沒有不知道希波克拉底的。在其他領域裡，如律師、證券商、會計師、審計師、評估師、推銷員等等，都拿希波克拉底誓言作為行業道德的要求。這個誓言成為人類歷史上影響最大的一個檔案之一。
希波克拉底誓詞中文版
醫神阿波羅，埃斯克雷彼斯及天地諸神為證，鄙人敬謹宣誓，願以自身能判斷力所及，遵守此約。凡授我藝者敬之如父母，作為終身同世伴侶，彼有急需我接濟之。視彼兒女，猶我弟兄，如欲受業，當免費並無條件傳授之。凡我所知無論口授書傳俱傳之吾子，吾師之子及發誓遵守此約之生徒，此外不傳與他人。
我願盡余之能力與判斷力所及，遵守為病家謀利益之信條，並檢束一切墮落及害人行為，我不得將危害藥品給與他人，並不作此項之指導，雖然人請求亦必不與之。尤不為婦人施墮胎手術。我願以此純潔與神聖之精神終身執行我職務。凡患結石者，我不施手術，此則有待於專家為之。
無論至於何處，遇男或女，貴人及奴婢，我之唯一目的，為病家謀幸福，並檢點吾身，不做各種害人及惡劣行為，尤不做誘姦之事。凡我所見所聞，無論有無業務關係，我認為應守秘密者，我願保守秘密。倘使我嚴守上述誓言時，請求神只讓我生命與醫術能得無上光榮，我苟違誓，天地鬼神共殛之。
誓詞英文原文
The Hippocratic Oath
Original, translated from Greek.
I swear by Æsculapius, Hygeia, and panacea, and I take to witness all the gods, all the goddesses, to keep according to my ability and my judgement, the following Oath.
To consider dear to me as my parents him who taught me this art; to live in common with him and if necessary to share my goods with him; To look upon his children as my own brothers, to teach them this art if they so desire without fee or written promise; to impart to my sons and the sons of the master who taught me and the disciples who have enrolled themselves and have agreed to the rules of the profession, but to these alone the precepts and the instruction.
I will prescribe regimens for the good of my patients according to my ability and my judgment and never do harm to anyone.
To please no one will I prescribe a deadly drug nor give advice which may cause his death.
Nor will I give a woman a pessary to procure abortion.
But I will preserve the purity of my life and my art.
I will not cut for stone, even for patients in whom the disease is manifest; I will leave this operation to be performed by practitioners, specialists in this art.
In every house where I come I will enter only for the good of my patients, keeping myself far from all intentional ill-doing and all seduction and especially from the pleasures of love with women or with men, be they free or slaves.
All that may come to my knowledge in the exercise of my profession or in daily commerce with men, which ought not to be spread abroad, I will keep secret and will never reveal.
If I keep this oath faithfully, may I enjoy my life and practice my art, respected by all men and in all times; but if I swerve from it or violate it, may the reverse be my lot.
誓詞的核心
簡短而洗鍊的的誓言，向世人公示了四條戒律：
