Ancient Greek has been said to have a form of morphosyntactic symmetry called mood attraction or mood assimilation where a subordinate clause was formally assimilated to the same mood as the matrix clause (i.e. an optative, indicative or subjunctive with certain temporal reference limitations). As counterproposal, this article uses a corpus study of Archaic (8th-5th century BCE) and Classical Greek (6th-4th century BCE) to demonstrate that this aspect of modal syntax is in fact pragmatically conditioned. Subordinate clauses in counterfactual mood attraction do not need the expected modal particle (an / ke(n)) because they obtain their counterfactuality via transfer of counterfactual implicature from the matrix clause. This transfer resembles how counterfactual matrix clauses receive counterfactual implicature from preceding counterfactual conditionals, because (i) transfer only takes place with temporally iconic subordinate clauses with a causal connection, (ii) the negative or positive polarity of the matrix clause is also transferred, and (iii) both the counterfactual optative (in Archaic) and indicative (in Archaic and Classical Greek) can be found in the matrix and subordinate clause, even asymmetrically in Archaic Greek. Furthermore, non-counterfactual mood symmetry with the optative or subjunctive is also pragmatically conditioned, as choosing a symmetrical mood in the subordinate clause has both a pragmatic and semantic motivation, just as when it is asymmetrically marked by mood in the so-called oblique optative.