Grammar of 'understanding' in informed consent: a Wittgensteinian diagnosis

Ethical accounts of informed consent require that patients understand the risks, benefits and alternatives of a proposed intervention. Recent philosophical work has examined what content must be understood and how much understanding is sufficient, but a prior question remains unresolved: what kind of concept 'understanding' is in this context. In current institutional practice, understanding is treated as a private mental state produced by receiving information. On this reception model, the consent process is organised around information transfer, and understanding is presumed to follow from adequate disclosure. This article argues that the reception model rests on a grammatical confusion that Wittgenstein diagnoses in Philosophical Investigations §§148-155. Wittgenstein shows that 'understanding' is not a mental process or inner event but a capacity demonstrated in use: to say that someone understands is to say something about what they can do, not about what has occurred inside them. Applied to informed consent, this analysis reveals that the consent process as standardly practised verifies understanding using the wrong kind of evidence, collecting self-reports about an interior state rather than demonstrations of a capacity. The diagnosis explains an otherwise puzzling empirical pattern: readability-focused consent interventions produce inconsistent improvements in comprehension, while demonstration-based methods such as teach-back succeed more consistently. The article develops four implications for consent process design: evaluating adequacy by demonstrated comprehension rather than disclosure completeness; adopting teach-back as the standard approach to verification; redesigning consent forms for elicitation rather than readability alone; and narrowing the conceptual gap between ordinary consent and formal capacity assessment.