949). Speech Act theory of Aristotle and Austin (1962) particularly is one that proposes relevant factors that limit computers' natural language processing capacity. They describe 'speech acts' as 'utterances' that a speaker pronounces as tools to interact in real-life situations where knowledge of the language and the appropriate contextual use of the speech acts within a given culture are required. 'Intentionality' as Franz Brentano suggests in his publication Psychology from an Empirical Standpoint (1973, first published 1874), is one significant feature distinguishing the psychological from the physical, mental acts from the external world, of the human minds which is clearly deficient in a machine. Despite the many intricately designed softwares using speech corpora data to create a controlled language to be used for a speech recognition system, identifying the words and phrase structures that regular people may use when interacting with the system, natural language processing has still not reached the desired results that computer linguistics are seeking to achieve.
It is mainly due to the inability of a machine to have a 'theory of mind' like humans bearing intentions and past experiences for future exchanges to be able to perceive the psychic tone, connotation in the dialogue of the speaker that computer linguistics face a serious challenge in developing models that can effectively generate a coherent natural language discourse between a computer and people. Aristotle's concept of 'mental inexistence', the notion that when one thinks of an object, one has an object 'in mind', but the object in mind does not 'exist' in the same way that the object in the world exists puts forward the disadvantage of a machine's imperceptions of human's 'emotives' like anger or shame from their statements. 'Performative utterances' are social acts reflective of a person's gender-related undertones, sentiments and seeming intentions depending on the speaker's apparent present physical state, cultural, ethnic and social background. These most likely are unable to be accurately perceived to mean something added by a machine as we know that although a computer might in theory be programmed with the sum total of all information there is to be had about the world, this does not mean that the computer 'understands' the world. 'Understanding' is an intentional phenomenon, along with perceiving, acting and learning. Computers merely manipulate symbols, and hence are incapable of being attributed with these intentional phenomena.
Critics of AI argue that computers are incapable of achieving the level of cognitive ability that humans exhibit. To this point, Searle (1969) made a distinction between strong AI and weak AI whereby Strong AI describes a system that is able to reason and perform as well as - or better than - a human. A strong AI system is conscious of itself and operates beyond a strict adherence to preprogrammed rules and algorithms.1 In his 'Minds, Brains and Programs' (1980), John Searle demonstrates that a programmed digital computer cannot have cognitive states such as understanding. He does this through a famously elegant thought experiment called the 'Chinese Room'