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Had optical perception not evolved into something more than sensory perception, into super-sensory perception, then the present period would never have had the courage to discover the spiritual in matter. There would have been no fundamental difference between a painting by Picasso [from Picasso's so-called 'abstract' period] and one by Paulus Potter [Dutch painter from the 17th century, famous for his painting of cows]
— THEO VAN DOESBURG