A very old idea about how to build a perceptual system
	• Start by learning some features of the raw sensory input. The features should capture interesting regularities in the input. • Then learn another layer of features by treating the first layer of features as sensory data. • Keep learning layers of features until the highest level “features” are so complex that they make it very easy to recognize objects, speech …. • Fifty years later, we can finally make this work!