Before Galileo, cannoneers aimed their cannons guided by the 2000-year old physics of Aristotle. Aristotle had explained the motion of falling bodies by attributing to all matter a purpose, or telos, the Greek word for “goal,” which was, in the case of physical matter, to move to the center of the earth. Drop a ball from a tower, without any impetus by you, and the ball falls toward the center of the earth as if driven there by an internal cause.
Everything had a telos and Aristotle explained everything teleologically, by referencing the thing’s purpose. Air had the purpose of rising, matter of moving to the center of the earth; a giraffe’s purpose was to prune the trees too tall for other animals to eat.
According to pre-Galilean ballistics, a cannon ball’s trajectory moved in a straight line, at the same angle the cannon was tilted, until the force from the gun powder wears off and then soon after the ball drops straight down, as its natural telos takes over.
In one of the most dramatic examples of “tinted glasses,” i.e., of theory coloring perceptual experience, drawings made by cannoneers from this time do not show what we now know thanks to Galileo would have been the path of the cannon balls, namely a parabolic shape.
Could they not just open their eyes and look? They did. They saw what their theory constructed for them.