Logical Subject meant ʻdoer of the actionʼ. It was called ʻlogicalʼ in the sense this term had had from seventeenth century, that of ʻhaving to do with relations between thingsʼ as opposed to ʻgrammaticalʼ relations which were relations between symbols.
- Halliday (1985), Pag. 34

There is no such thing as a general concept of ʻSubjectʼ [...] In order to take account of this, we will replace the earlier labels by separate ones which relate more specifically to the functions concerned [...] logical Subject: Actor.
- Halliday (1985), Pag. 35