The most fundamental mainstream function of the word 'can' is to denote an agent's ability or capacity to perform an action. This capacity may be inherent, learned, or afforded by circumstances. As noted in the definition by Merriam-Webster, 'can' is primarily used to indicate that a subject is 'physically or mentally able to' do something. Unlike lexical verbs, 'can' functions as a modal auxiliary verb, meaning it does not change form for person or number and is followed by the bare infinitive of the main verb without the particle 'to'. Linguists categorize this as 'dynamic modality,' which centers on the properties of the subject. For instance, 'She can speak four languages' indicates a cognitive ability, while 'This bridge can support ten tons' indicates a physical property. This usage remains the most stable and frequent application of the word across all dialects of English, serving as a critical tool for describing potentiality and competence.
Deontic Modality and the Permission Debate
A second major mainstream perspective involves the use of 'can' for requesting or granting permission, a category known as 'deontic modality.' Historically, prescriptive grammarians maintained a strict distinction between 'can' (for ability) and 'may' (for permission). However, modern descriptive linguistics and the entry from the Cambridge Dictionary emphasize that 'can' is now standard for 'asking for or giving permission,' particularly in neutral or informal contexts. While 'may' persists as a more formal alternative, mainstream linguistic consensus acknowledges that 'can' has largely superseded it in daily communication. This shift is viewed not as an error, but as a natural evolution of English where the context usually clarifies the intent. Using 'can' for permission is now considered standard English in both American and British varieties, though 'may' is still preferred in highly formal writing or legalistic settings to ensure maximum precision and etiquette.
Epistemic Possibility and Pragmatic Functions
Beyond ability and permission, 'can' is employed to express 'epistemic possibility'—the theoretical likelihood of an event occurring based on general facts or circumstances. This is often used to describe general truths or recurring situations, such as 'The desert can be freezing at night.' In this context, it differs slightly from 'might' or 'could,' which often imply a specific, uncertain event in the future. Furthermore, 'can' serves vital pragmatic functions in social interaction, such as making requests, offers, or suggestions (e.g., 'Can you help me?' or 'We can try that later'). These functions demonstrate the word's versatility in managing social dynamics and interpersonal expectations. In these scenarios, 'can' functions as a 'politeness marker,' though it is often considered less tentative or indirect than 'could.' Modern corpus linguistics shows that 'can' is one of the most frequently used modal verbs precisely because it bridges the gap between literal capacity and social negotiation.
Conclusion
The mainstream view identifies 'can' as a versatile modal auxiliary verb essential for expressing ability, permission, and possibility. While historical distinctions between 'can' and 'may' persist in formal education, modern linguistic practice and reputable lexicographical sources recognize that 'can' is the primary and standard choice for both capacity and permission in contemporary English.
Alternative Views
The Epistemic Root: Knowledge as Capability
The word 'can' is derived from the Old English 'cunnan', meaning 'to know' or 'to have mental capacity.' An unconventional view posits that capability is purely a function of knowledge rather than physical strength or external permission. In this framework, saying 'I can do this' is an assertion of one's deep understanding of the mechanics of the task. This perspective, often found in esoteric interpretations of language, suggests that the modern separation of 'knowing' from 'doing' is a late-stage linguistic corruption. By reclaiming 'can' as a synonym for 'know,' proponents argue we can shift our self-perception from passive biological machines to active cognitive agents whose limits are defined solely by the boundaries of their comprehension. This view challenges the physicalist mainstream by asserting that the mind's grasp of reality is the sole determinant of what is actually possible for the individual.
Attributed to: Esoteric linguistic circles and etymological traditionalists
Deterministic Placeholder: The Semantic Error of Potentiality
From the perspective of hard determinism, the word 'can' is viewed as a linguistic artifact of human ignorance. If the universe is a closed system of cause and effect, the concept of 'possibility' is an illusion. Mainstream definitions, such as those found at (https://www.merriam-webster.com/dictionary/can), describe 'can' as having the power or ability to act. However, radical determinists argue that we only use 'can' when we lack sufficient data to describe the inevitable 'must.' In this view, 'can' acts as a semantic buffer that preserves the illusion of free will; it is a way for the brain to process complex causal chains it cannot yet fully calculate, transforming a singular trajectory into a perceived field of options that do not actually exist in a fixed physical sense.
Attributed to: Hard Determinists and Neuro-Philosophers
Modal Realism: Can as a Portal to Alternate Realities
In the context of modal realism, 'can' is not a description of a hypothetical state but a reference to actual existences in parallel universes. When an individual states that something 'can' happen, they are identifying a property that exists in a subset of possible worlds. This view, which stems from radical interpretations of the philosophy of David Lewis, suggests that 'can' acts as a linguistic bridge between our specific world-line and the totality of the modal space. Instead of being a measure of probability within this world, 'can' is a literal description of occurrences in the multiverse. This perspective shifts 'can' from a modal verb of potentiality to a descriptive verb of multiversal reality, where every capability mentioned is a factual event occurring in a real, albeit distant, branch of existence.
Attributed to: Modal Realists and radical proponents of the Many-Worlds Interpretation
The Conflation of Natural and Social Law
Post-structuralist critiques suggest that 'can' is a primary tool for social engineering because it conflates inherent ability with external permission. While dictionaries like (https://dictionary.cambridge.org/dictionary/english/can) note that the word is used for both power and permission, this viewpoint argues that this ambiguity is intentional and restrictive. By using the same word for a physical act (I can jump) and a social decree (You can leave), the language forces the individual to subconsciously equate social boundaries with natural limitations. This perspective suggests that 'can' serves to internalize authority, making external prohibitions feel as unchangeable as the laws of physics. It is viewed not as a word of empowerment, but as a linguistic cage that masks the distinction between what is physically impossible and what is merely socially forbidden.
Attributed to: Post-structuralist and radical sociolinguistic theorists
References
Huddleston, R., & Pullum, G. K. (2002). The Cambridge Grammar of the English Language. Cambridge University Press.
Quirk, R., Greenbaum, S., Leech, G., & Svartvik, J. (1985). A Comprehensive Grammar of the English Language. Longman.
Merriam-Webster. (n.d.). Can. In Merriam-Webster.com dictionary.
Cambridge University Press. (n.d.). Can. In Cambridge Dictionary.
Swan, M. (2016). Practical English Usage (4th ed.). Oxford University Press.
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