Essentialism reigned for 2,000 years.
Beginning with Aristotle, philosophers had an almost standard belief that all things and beings had an essence that defined their purpose and existence. For instance, a knife's essence is the blade, and its purpose is to cut. They argued over what essence was, but never about whether things or people have an essence.
Early Christianity resonated with this Aristotelian idea because according to the Bible, people also have an essence: the image of God. Genesis 1:27 says, "So God created mankind in his own image, in the image of God he created them; male and female he created them." Our essence gives us purpose, namely glorifying God. "So whether you eat or drink or whatever you do, do it all for the glory of God" (1 Corinthians 10:31).
However, beginning in the mid-19th century, philosophers began to question the essentialist paradigm and began to believe that existence came first and that purpose was determined by the individual later. We don't begin with a purpose-giving essence. We choose our essence and purpose — whatever we want it to be, no matter how evil or ignorant of our creator — once we exist. So, they were called existentialists.
But they weren't the first to think that way.
Ezekiel 28:11-19 is one of the handful of essential passages in the Bible for a study of Satan. It is specifically a criticism of the king of Tyre, but by the third verse of the passage, it becomes clear God seems to be talking about someone else since there is no way the human king of a city in 600 BC could have been "in Eden, the garden of God." (Ezekiel 28:13) Instead, it becomes clear we are reading about the being who has influenced the king of Tyre, which seems to be Satan himself.
Verse 13 not only places Satan in the Garden of Eden, but also ascribes to him nine precious stones that he wore. The high priest of Israel also wore these stones, along with three others, on his breastplate in his official garb. It would seem, then, that Satan may have had a special, priestly or representative purpose. Verse 14 confirms this. "You were anointed as a guardian cherub, for so I ordained you." "I ordained you" and "I set your purpose" are roughly equivalent.
Putting this information together, it seems that Satan himself was created with a purpose. God wanted him to perform a specific function and to fulfill a specific purpose. We don't know what that purpose was for sure, but it's clear from the passage it was a unique and important purpose that involved representing God's glory in a particularly spectacular way.
But Satan chose a different purpose. Rejecting the essence endowed to him by his creator, Satan elected to choose his own purpose. Satan became the first existentialist.
Isaiah 14:12-20 is another crucial Old Testament passage about Satan, and it reveals the purpose Satan chose, which led to his fall. "(Satan) said in (his) heart, 'I will ascend to the heavens; I will raise my throne above the stars of God; I will sit enthroned on the mount of assembly ... I will make myself like the Most High'" (Isaiah 14:13-14).
Driven by self-determination and autonomy, Satan became the ostensible commander of his own destiny. He became an end unto himself and decided he would set his own rules. He decided that his own glory was sufficient and qualified him to be in charge instead of God. All of this happened before his first words in the Bible, "Did God really say ...?" (Genesis 3:1). He went on to tell Eve that God's motives weren't good. According to Satan, God just wanted to keep Adam and Eve from being the masters of their own destiny as well. He claimed that when they ate the fruit, Adam and Eve would become "like God" (Genesis 3:5). So Eve took a bite and became the second existentialist. Instead of living according to the essence her creator bestowed upon her, she chose her own purpose.
So the question remains before us today: Will we attempt to be the masters of our own destiny? Will we choose our own way? Our own glory? It seems the most evil being in all of creation became that way because he chose these things. If we want to be good people, and if we want to live in a good society, it seems foolish to make the same decisions as the most evil being that ever existed. Instead, allow God to be the master of your destiny. Choose his way and his glory.