I should probably point out first, this may go against what you currently believe or understand based upon modern Christianity. There are certain things that are widely accepted as theologically sound by theologians that just never seems to be transmitted to most Christians. This will be one of those things, so while I expect to raise a few eyebrows, rest assured this is fully researched and is pretty much the view you would find espoused by respectable theologians and seminaries.
Lately I’ve been looking at some of the books that have been by tradition attributed to Moses. While I don’t attribute them to Moses as that is unlikely, I do believe they are inspired and were written to make some very poignant theological statements to the people groups found in the nations surrounding Israel. One of the interesting observations is that the serpent who tempted Eve is not referred to as satan (Genesis 3:1-19). In fact, in the old testament, he isn’t always referred to as a serpent but sometimes as a cherub (Ezekial 28:12-19). Only much later in Revelation is satan clearly equated with the serpent; why is that?
Satan is actually not a person per se in the old testament, but a role. In fact, God takes on the role of satan when he becomes angry with David and causes him to take a census. In 1 Chronicles 21:1 satan rises up against Israel, but the parallel in 2 Samuel 24:1 the anger of the Lord burns against Israel whom he wishes to harm. There is no way for satan to be a proper sole entity given the contextual usage. Even in Job, the usage of “satan” is in reference to a role. The basic office or role is an opposer or one which causes others to stumble.
Christ himself refers to Peter as satan in Matthew 16:23, not because he was possessed or a pawn of a singular spiritual entity, but rather because his desire for Christ to live was in opposition to the divine will of God. Throughout the new testament there is also reference to the devil, which carries on essentially the same meaning as satan in the old testament. The new testament does begin to take on wording in which entities in opposition to God are a cosmic-arch-enemy of sorts, but this seems more in parallel with his arch enemies being the sons of God whom he gave humanity to following the Babel incident (this is made clear in Deuteronomy 32:8; furthermore, their opposition to God is apparent in Psalm 82).
If the old testament is any indication, and if we are to believe the works to be divinely inspired, then we must presume that God has a particular penchant for using popular culture iconography. For example, the throne which Ezekiel sees twice is absolutely rife with iconography as would be seen on thrones around the region. Likewise, Revelation in particular adopts certain popular cultural references in which apocalyptic texts have an arch-nemesis figure (amongst a myriad of references aimed at showing God is God while Domitian is not). Now, this brings us back to the garden; the serpent certainly plays the role of satan and fills the literary requirement of arch enemy but the role certainly has historically and continues to be played out by a multitude of both sons of God (and lesser divine creatures such as angels and cherubs) and sons of man (humans).
Moving past solely the intellectual and theological, the implications for how we live our lives are massive. If we are not cautious, we can very much be satan to or for our fellow Christians as our actions and words oppose God’s divine will for them. It could be as simple as the way in which we speak, it could be the way in which we drive, or even when we discourage people from acts of charity or missions (conversely, it could be from encouraging people into such things be they contrary to God’s divine will). This is why it is all the more important to know God and pray continuously to be able to see others as God sees them, love others as God loves them, and know God’s will. Christ, despite being fully God in his own right, continued to pray regularly to know and understand the divine will. How much more we should follow this example!