Hubert Dreyfus was a critic of artificial intelligence research. In a series of papers and books, including Alchemy and AI (1965), What Computers Can't Do (1972; 1979; 1992) and Mind over Machine (1986), he presented a pessimistic assessment of AI's progress and a critique of the philosophical foundations of the field. Dreyfus' objections are discussed in most introductions to the philosophy of artificial intelligence, including Russell & Norvig (2021), a standard AI textbook, and in Fearn (2007), a survey of contemporary philosophy.
Dreyfus argued that human intelligence and expertise depend primarily on yet-to-be understood informal and unconscious processes rather than mathematically elegant symbolic manipulation or similarly simplistic neural nets and that these essentially human skills cannot be fully captured in formal rules. His critique was based on the insights of modern continental philosophers such as Merleau-Ponty and Heidegger, and was directed both at the first wave of AI research which tried to reduce intelligence to high level formal symbols and at the connectionist simulation of neural nets.
When Dreyfus' ideas were first introduced in the mid-1960s, they were met in the AI community with ridicule and outright hostility. By the 1980s, however, many of his perspectives were partially rediscovered by researchers working in robotics and the new field of connectionism—approaches now called "sub-symbolic" because they eschew early AI research's emphasis on high level symbols. In the 21st century, statistics-based approaches to machine learning attempt to imitate the way that the brain uses unconscious processes to perceive, notice anomalies and make quick judgements. These techniques are highly successful and are currently widely used in both industry and academia. Historian and AI researcher Daniel Crevier writes: "time has proven the accuracy and perceptiveness of some of Dreyfus's comments." Dreyfus continued to object to current AI until his death in 2017.