voluntarius (ἐθελούσιος, ἐθελοντής, from one’s own choice): volens (of one’s own will; opposed to coactus): non coactus, non invitus (without compulsion or external incitement, ἑκών, ἑκούσιος). ☞ spontaneus (αὐτόματος) and ultroneus (αὐτοκέλευστος) differing as sponte and ultro, not identical with voluntarius, occur first in Sen., Ep., and Quint., 2, 59, 7, and were probably formed by Sen. for his philosophical style. Instead of them we usually find sponte and ultro with a participle suited to the context; e.g., a voluntary motion, motus sua sponte factus (for motus spontaneus in Sen.), etc.