Deep Learning has revolutionised Pattern Recognition and Machine Learning. It is about credit assignment in adaptive systems with long chains of potentially causal links between actions and consequences.
Koen Smets, Bart Goethals, and Brigitte Verdonk. Proceedings of the Association for the Advancement of Artificial Intelligence (AAAI) Workshop on Wikipedia and Artificial Intelligence: An Evolving Synergy (WikiAI08), page 43--48. AAAI Press, (2008)