It seems to be increasingly common for students, and others, to use ‘as such’ as a replacement for ‘therefore’ only to be corrected without really knowing why. If you think ‘as such’ and ‘therefore’ have the same meaning, read on.
‘Therefore’ is a conjunction (a part of speech that joins words, phrases, clauses or sentences) that according to The Macquarie Dictionary means ‘in consequence of that’, ‘as a result’ or ‘consequently’.
‘As such’ also acts as a conjunction but is different grammatically. The Macquarie Dictionary defines ‘as such’ to mean ‘being what is indicated’, ‘in that capacity’ or ‘in itself or themselves’. ‘Such’ in the phrase ‘as such’ acts as a pronoun (a part of speech used in the place of a noun).
Confused? Basically, this means that when using ‘as such’ there must be an ‘antecedent noun’, that is, something already mentioned that ‘such’ refers to. You can test for whether ‘as such’ makes grammatical sense by asking ‘As what?’ to see if there is an antecedent noun or noun phrase that can give the answer. For ‘therefore’, see if it makes sense to use ‘as a result’ instead.
Rex was leader of the pack and, as such (As what? As the leader of the pack.), expected obedience from the other dogs. (no problem here)
Rex was leader of the pack and, therefore (as a result), expected obedience from the other dogs. (no problem here either)
Lemons contain citric acid and, therefore (as a result), are very sour. (also no problem)
So far so good, but replacing ‘therefore’ with ‘as such’ in this sentence causes a problem.
Lemons contain citric acid and, as such (As what? One can’t answer this with a noun), are very sour. (problem! There is no antecedent noun for ‘such’)
Cats are curious and, as such (As what? One can’t answer this with a noun.), can get themselves in predicaments. (problem!)
Cats are curious animals and, as such (As what? As curious animals.), can get themselves in predicaments. (no problem)