Final answer:
The physical aspects of humanity are seen as good because they are a part of divine creation, fulfill human nature, and are integral to spiritual and moral development.
Step-by-step explanation:
Three reasons that the physical aspects of a man's being are good and not a source of evil within him could be based on various philosophical and religious perspectives. Firstly, the physical body and the world around us can be seen as a manifestation of divine consciousness, where everything in the physical realm has an intrinsic goodness as part of a larger cosmic order, which is to be respected and taken care of. Secondly, the very fact that humans can understand what is good for them according to human nature, suggests that by fulfilling their natural functions they achieve well-being and avoid committing evil. Thirdly, embracing the full potential of human rationality to improve and enjoy life can be considered a positive use of physical existence, aligning with the argument of upholding human rights to achieve one's full potential through the rational mind.
From St. Augustine's perspective, although humanity fell from grace, the physical remains part of God's creation, inherently designed to grow towards spiritual love. Whereas, according to the Irenaeus' teleological view, the physical being serves a developmental role in soul-making and spiritual growth. Moreover, the idea that a perfect being would have no evil suggests that the presence of physical being, despite its flaws, is part of a greater plan that aligns with a perfectly good deity's intention for soul-making and facing challenges that lead to higher moral and spiritual states.
In conclusion, the physical aspects of a man are seen as fundamentally good because they are part of divine creation, aid in fulfilling human nature, and play a critical role in the journey towards greater spiritual and moral development.