The insurgent mentioned by Gamaliel as having led 400 men, boasting himself to be somebody of importance. Slain at last. His followers were dispersed (Acts 5:36). Josephus describes such a Theudas (44 A.D.), under Claudius, i.e. ten years later than Gamaliel's speech. As Theudas preceded Judas the Galilaean according to Luke, he must have revolted at the close of Herod's reign (for Judas appeared in 6 A.D. after Archelaus' dethronement), a very turbulent period in which Josephus names three disturbers, leaving the rest unnamed; among the latter was probably Theudas; it is not strange that 50 years later another Theudas, an insurgent in Claudius' time, should arise.
Or Luke's Theudas may be Josephus' Simon, one of the three whom, he names in the turbulent year of Herod's death (B. J. 2:4, section 2; Ant. 17:10, section 6; 12, section 6; 20:4, section 2), Herod's slave who tried to make himself king in the confusion consequent on the vacancy in the throne. He corresponds to Luke's description of Theudas in his lofty notion of himself, in his violent death which is not true of the other two insurgents, in the fewness of his followers. Thus, Theudas would be his name, long borne, and so best known to Gamaliel and the Sanhedrin at Jerusalem; Simon the name wherewith he set up as king, and so given by Josephus writing for Romans.