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The price of metaphor is eternal vigilance.
 Arturo Rosenblueth
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No substantial part of the universe is so simple that it can be grasped and controlled without abstraction. Abstraction consists in replacing the part of the universe under consideration by a model of similar but simpler structure. Models, formal and intellectual on the one hand, or material on the other, are thus a central necessity of scientific procedure.
 Arturo Rosenblueth
					 
