Aristotle decided observation was irrelevant? Are you joking? If we are going to base physics on how nature is actually experienced, then Galileo is the one ignoring observation. Galilean physics are based on ideal geometrical models, not actual observation, where friction and resistance are impossible to do away with. Aristotle’s is precisely an experiential physics, while Galileo’s is a mathematical physics.
I find it disturbing that so many of you science geeks dismiss Aristotle as a historical curiosity. Thomas Kuhn points out that this historical ignorance is the biggest obstacle to a full understanding of what science is and how it works.
Formal causes are actually forcing their way back into physics (information theory) and biology (autopoiesis, self-organization, etc.), despite materialistic pretenses. Final causation has also been part of physics for 150 years (thermodynamic energy gradients behave teleologically, moving toward equilibrium), and is obviously a required element in any description of a living system (though biologists, after Mayr, tend to call it “teleonomy”).
Just keep in mind as you self-assuredly brush Aristotle into the dust bin of history that in 100 years time, much of what passes for science today will be similarly dismissed as superstition (at least unless scientists begin to receive better education in history).