Halliday & Matthiessen (1999: 60-1):
Some 'simple things' are metaphorical; the remainder are referred to as 'ordinary', and these are either conscious or non-conscious (this is the distinction that is actually made in the semantic system, not animate/inanimate or human/non-human): see Plate 6.
Non-conscious ordinary things are distinguished along more than one dimension, but the categorisation given here can be taken as primary, in the sense that it is the one that seems to have the clearest reactances in the grammar.
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When we construe any organism as being able to see, for example, we are construing it as conscious, since perception is a type of mental process.