Each of these philosophers had very different ideas about how the world was created, how it works, and what man's role in it was. If you consider how the philosophers are looking in the illustration above, it's easy to figure out how they saw things.
• Plato
Plato did not value the material world, and did his best to shut out the senses which he thought would pull him away from the spirit realm (that's why his eyes are closed). For Plato only the spirit realm was important and this world with its bodily form was a prison of the soul—anything that changed was not eternal and therefore bad. One could learn nothing about the Ultimate creator by observing this world because the creator could not be soiled by touching matter. He had to create other gods to create the material world since he could not interact directly with matter.
• Aristotle
Aristotle saw the world as constantly changing, and thought that was evidence that motion was the underlying basis of the world. The Prime Mover (the Unmoved Mover) started all motion but was not involved in the result. However, if one observed nature, one could learn about the motions the Prime Mover used and therefore learn about the Prime Mover himself. The Prime Mover used eternal uncreated matter to stamp the Forms starting the motion and then became disinterested in interacting further.
• Plotinus
Plotinus saw the world as part of the essence of the One. That means that the material universe was a part of the body of the One (or god) and all material elements of the material world were made up of the essence (substance) of the One. While observing nature could not necessarily raise you to a higher spiritual plane, it was necessary to start in the material world to "return" to oneness with the One. Hinduism casts a shadow on the ideas of Plotinus, and a form of his mysticism was brought into the Roman Catholic and Greek Orthodox churches through manuscripts discovered around 500ad thought to be written by the Dionysius of Acts 17. They were not, and the ideas of the Pseudo-Dionysius were borrowed from Proclus, who died in 480ad, just 20-50 years or so before the manuscripts were discovered.
• Democritus
Democritus saw the world as the result of chance. Matter was eternal and uncreated, there was no spirit realm. He is famous for saying, "Nothing exists except atoms and the empty space between them. Everything else is opinion." The term he used—"atoms"—was just Greek for "not divisible," i.e., the smallest particle of matter. He had no concept of atoms as we know it, and the term was simply borrowed by scientists in the 19th century. For Democritus, there was no god, no spirit realm, no soul, only the random chance collisions of eternal particles of matter.
