The Image of God
God created human beings in his own image (Genesis 1.27). That is, God created human beings to love and enjoy him in perfect fellowship, without sin, being in some sense like God and representing God (Genesis 1.31). Male and female were created in the image of God, and together fully reflect the image of God (Genesis 2.8, Ephesians 5.22-33). It is this fact - that they have been created in the image of God - that makes human beings unique in all of God's creation, and makes their value as created beings distinct from other elements of creation.
The Purpose of Humanity
Since God lives and exists in perfect relationship with himself, needing no other relationship than that which is perfected int he godhead, he had no need to create human beings. He therefore created human beings for the purpose of glorifying himself (Revelation 7.9-10). This glory is made evident through the ways God relates to his created beings and the ways in which they praise him for his glorious deeds (Psalm 78.4). Through his interactions with human beings, God shows himself to be kind, merciful, forgiving, just, loving, etc. (Exodus 34.5-7, Psalm 18.25, 107.1, 145.9), bringing glory to himself through the display of these attributes. Even through God's just judgment of sin (and sinners), God is shown to be great in that he rightly deals with evil (Psalm 7.6 89, 27-29, Hebrews 10.30).
The Nature of Sin
Sin is any and every thing that is contrary to the nature and will of God. It is the inclination of human beings to act and think independently of God's will and revelation (Genesis 3.6, Romans 3.23). Sin separates the offender from the Holy God (Isaiah 59.2). Through the Fall, the entire human race was plunged into sin and is hopelessly lost in it (Romans 5.12, 1 Corinthians 15.22, Romans 6.23).
God does not tempt or force human beings to sin (James 1.13). Rather, he allows human beings to follow the desires of their sinful, fallen hearts. God is sovereign over humankind's sinful activities, however, in that he chooses to allow, or not allow, sinful activities to take place (John 19.10-11, Acts 2.22-23, 4.27-28). In this sense, while God remains sovereign over sin, he cannot be accused of having sinned or being evil himself, and human beings bear the full responsibility for their sin.
The Fallen Nature and Effects of Sin
Although God created human beings as morally upright (Ecclesiastes 5.29), they were led away from the truth of God's will and revelation by Satan (Genesis 3.1). Having been given freedom by God, in allowing themselves to be deceived, they chose to act against God's word and therefore declared their independence from him. In this sense, human kind fell from their state of sinlessness and fellowship with God (2 Corinthians 11.3). All human beings since Adam and Eve, therefore, in some mysterious way, have inherited a sinful nature and similarly suffer the consequences of such a nature, namely separation from God int he spiritual sense (Romans 5.8, Hebrews 11.6, Isaiah 64.6). All people have been corrupted by this nature and are totally depraved, enslaved to sin, and unable to overcome its effects and control by their own power (Isaiah 64.6, Ephesians 2.8-9). The physical result of this fallen nature is that of death, sickness, and decay (Genesis 3.14-19). All suffering, therefore, is a result of the fallen nature of human beings (Genesis 3.16-19, Romans 5.12)