<P> The medieval Persian philosopher and physician Muhammad ibn Zakariya al - Razi believed in a close relationship between conscience or spiritual integrity and physical health; rather than being self - indulgent, man should pursue knowledge, use his intellect and apply justice in his life . The medieval Islamic philosopher Avicenna, whilst imprisoned in the castle of Fardajan near Hamadhan, wrote his famous isolated - but - awake "Floating Man" sensory deprivation thought experiment to explore the ideas of human self - awareness and the substantiality of the soul; his hypothesis being that it is through intelligence, particularly the active intellect, that God communicates truth to the human mind or conscience . According to the Islamic Sufis conscience allows Allah to guide people to the marifa, the peace or "light upon light" experienced where a Muslim's prayers lead to a melting away of the self in the inner knowledge of God; this foreshadowing the eternal Paradise depicted in the Qur'ān . </P> <P> Some medieval Christian scholastics such as Bonaventure made a distinction between conscience as a rational faculty of the mind (practical reason) and inner awareness, an intuitive "spark" to do good, called synderesis arising from a remnant appreciation of absolute good and when consciously denied (for example to perform an evil act), becoming a source of inner torment . Early modern theologians such as William Perkins and William Ames developed a syllogistic understanding of the conscience, where God's law made the first term, the act to be judged the second and the action of the conscience (as a rational faculty) produced the judgement . By debating test cases applying such understanding conscience was trained and refined (i.e. casuistry). </P> <P> In the 13th century, St. Thomas Aquinas regarded conscience as the application of moral knowledge to a particular case (S.T. I, q. 79, a . 13). Thus, conscience was considered an act or judgment of practical reason that began with synderesis, the structured development of our innate remnant awareness of absolute good (which he categorised as involving the five primary precepts proposed in his theory of Natural Law) into an acquired habit of applying moral principles . According to Singer, Aquinas held that conscience, or conscientia was an imperfect process of judgment applied to activity because knowledge of the natural law (and all acts of natural virtue implicit therein) was obscured in most people by education and custom that promoted selfishness rather than fellow - feeling (Summa Theologiae, I--II, I). Aquinas also discussed conscience in relation to the virtue of prudence to explain why some people appear to be less "morally enlightened" than others, their weak will being incapable of adequately balancing their own needs with those of others . </P> <P> Aquinas reasoned that acting contrary to conscience is an evil action but an errant conscience is only blameworthy if it is the result of culpable or vincible ignorance of factors that one has a duty to have knowledge of . Aquinas also argued that conscience should be educated to act towards real goods (from God) which encouraged human flourishing, rather than the apparent goods of sensory pleasures . In his Commentary on Aristotle's Nicomachean Ethics Aquinas claimed it was weak will that allowed a non-virtuous man to choose a principle allowing pleasure ahead of one requiring moral constraint . </P>

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