It is thus the obligation of every person to ponder why he was created. When one does so, he may realize that his lifestyle and actions are not all they should be, neither intellectually, emotionally, nor with regard to proper conduct. [He may even come to realize that he is acting in a manner totally antithetical to ideal behavior;] he is always preoccupied with his physical needs, and pays little heed to matters of spiritual import. Such conduct truly coarsens a person.
Reflecting on such matters leads a person to desire repentance, and causes him to change his ways. He will begin following the path of Torah and mitzvos with proper reverence.
This, then, is the meaning of the verse: "The end of the matter, all having been heard, fear the A-lmighty and observe His commands, for this is the whole of man." The main reason for G-d's uniting of the spiritual soul and the physical body a unification of total opposites is so that man will fear the A-lmighty and observe His commands.
The union of body and soul is a binding of the very highest to the very lowest, as indicated by the verse:1 "Of the last [lowest of levels] and the first [highest of levels] have You formed me."
Man's body is called2 "the last" since it is even lower than the lowest animal.3 Concerning the bodies of animals our Sages say:4 "They were created in a whole and complete state." Concerning man's body, however, the verse states:5 "Your eyes beheld a shapeless mass."
In contrast, man's soul is deemed "the first,"6 for it comes from the greatest spiritual height. Thus man is a composite of the highest levels of spirituality and the lowest levels of corporeality, the corporeal being even more material than the merely physical. This is why we observe that a person with base tendencies may behave in a manner more evil than even the worst beast.7
Conversely, man's soul possesses such a lofty capacity that it can propel one to the greatest spiritual heights. All these sublime levels are achieved through Torah study and the performance of mitzvos with proper reverence.
This is the meaning of the words: "The end of the matter, all having been heard [and understood]...." Man, as an intelligent being, hears and understands how the existence of all creatures proclaim [the utter necessity of] fearing the A-lmighty, and observing His commands.
In summary: G-d created man as a composite of ultimate spirituality and ultimate corporeality. Therefore, corporeal man has base desires, but can also attain the greatest spiritual heights by observing Torah and mitzvos with proper reverence.