What makes the work of the Hebrew prophets unique is that they had been called by God for a purpose. In Genesis 22:11 the angel of the Lord calls Abraham, in 1 Samuel 3:4 the Lord called Samuel, but in Isaiah 6:8 the Lord asks for a volunteer and Isaiah says, “Here am I; send me.” One could see that although God sometimes called individuals directly to be prophets like in the case of Abraham and Samuel, sometimes he leaves the call or invitation open for a person to take like in the case of Isaiah.
As a student of classical civilization and western antiquity, I can attest to the fact that the Ancient Greek prophets had an extremely different approach to prophecy in contrast. Instead of God calling the prophet for a duty or purpose like in the case of the Hebrew prophets instead the Greek prophets would do things such as craft Gods, worship them, and arrive at divine revelation through observation of nature. The purpose of the work of the Greek prophets was to attempt to seek a message or even the will of God through careful probing and searching for an answer to their questions.
In ancient Greece every city-state (or polis) was defined by the distance a person could see in all directions from the highest point in the city, and every polis thus had a center for its government and for its God. Every city-state was thus unique with a different God as central to the operation, culture, and government of the people. Although many in Greece would have broken away from the mainstream worship of the city’s patron god to develop their own God’s for worship, revelation, and such, the competitive trend for Ancient Greek prophets would have been to interpret the will of their city-state’s patron God for the people in order to be the greatest middle-man between the people and the central God of the polis.
Although the Ancient Greek business of prophecy would have been rooted in finding solutions to problems that afflicted the people and positioning one’s self at the center of the system by having predictions that outdo the competition, the Hebrew approach was simply to only take a position as a prophet if God called the prophet to duty. In fact the Hebrew approach to prophecy was so much different than the competitive Greek approach that sought solutions to real world problems that Ezekiel 4:12 records God commanding Ezekiel to bake and eat his food in front of the people while using human excrement as fuel. From such examples one would conclude that the Hebrew prophets did their work out of a genuine duty to God whereas the Greek prophets would have had much to gain in comparison in terms of respect, power, and even income for their efforts to discern the will of the gods.