The son of James Peddie, a brewer, by his second wife, Ann Rattray, he was born at Perth, Scotland on 10 February 1758.

[1] Towards the end of 1782, against opposition, Peddie was appointed to the Bristo Street Secession chapel in Edinburgh, and took this position in April 1783.

[3] It continued from 1799 to 1815, and decided the legal position of the party New Light: Peddie gave it his zeal and energy.

[1] In the early days of the controversy, attempts were made by opponents to associate the New Lights with the friends of the French Revolution.

Peddie communicated with William Pitt the younger through Pulteney, and Henry Dundas referred to the New Lights as "loyal citizens, who had been calumniated.

Peddie's best-known work was a controversial pamphlet, against an attack of 1799 by William Porteous, The New Light Examined; or Observations on the Proceedings of the Associate Synod against their Own Standards.

Peddie's reply A Defence of the Associate Synod against the Charge of Sedition, addressed to William Porteous, D.D.

[1] He became an advocate of religious voluntaryism in the United Secession Church, with Hugh Heugh, across all Scottish Protestantism.