A state of a person or a relation between people that is not expressed, or one of which the subjects may even be unaware, but which can be inferred from their other capacities and activities. An agent able to construe an indefinite number of sentences of a language may be said to have tacit knowledge of the grammar of the language. Someone who voluntarily remains within the jurisdiction of a state is said by Locke to have tacitly consented to its laws. Tacit communication is the unexpressed recognition of the position of others that leads to strategies for common activity (see convention). The notion reflects the fact that people often behave ‘as if’ they have the described knowledge, or have made the consent or communication in question. But attributing further psychological reality to the concept is problematic: for example, Hume criticized Locke's political application of the notion on the grounds that the subject typically has nowhere else to which it is possible to go, and so is not so much behaving as if consenting to the authority of the state, but is behaving as if having to make the best of a possibly bad job.