Halliday & Matthiessen (2014: 257):
Like all other experiential systems, the system of type of sensing construes experience as indeterminate: the four different types of sensing shade into one another. For example, perception shades into cognition, with I see coming to mean not only ‘I perceive visually’ but also ‘I understand’. And cognition shades into perception with clauses where remember serves as the Process; unlike ‘cognitive’ clauses in general such clauses can be construed with a macrophenomenal Phenomenon …