He began his career studying psychology under Alurin. He became tired of it when he found there were no facilities on Terminus to pursue it, so went into politics instead.

He controlled the editorial policies of The Terminus City Journal, a newspaper, using it as a way to influence trends and people. He eventually was elected Mayor of Terminus. Despite the office's lack of official power, governing authority under the Foundation's charter being vested in the Board of Trustees of the Encyclopedia, Hardin had a substantial influence on the Foundation's foreign relations.

Hardin participates in the meeting of Anselm haut Rodric, an envoy from Anacreon, with Dr Lewis Pirenne, Chairman of the Board of Trustees. Shortly after, Lord Dorwin visits on behalf of the Empire. Lord Dorwin effectively promises no support for the Foundation, and meanwhile, concludes treaties with Anacreon, Smyrno and the other surrounding systems, that give them a large amount of autonomy. Hardin can see this is leaving Terminus without any military support and at the mercy of the surrounding systems. Hari Seldon's first appearance in the time vault gives Hardin the clue he needs to solve the crisis. He engineers a bloodless coup leaving him in complete control of Terminus and thus of the Foundation.

Hardin plays Anacreon against its neighbors by pointing out that allowing Anacreon to control the Foundation will render it militarily invincible. The other kingdoms force Anacreon to leave Terminus as an independent self-governing planet. Then, Hardin agrees to share the Foundation's vital scientific knowledge with the kingdoms, but under the guise of a religion - "Scientism" - which the Foundation controls. In this way, he steers the Foundation through the first crisis, and consolidates his own power at the same time.

After a period of 30 years or so, another crisis appears when the Kingdom of Anacreon under Prince Regent Wienis, the power behind the throne of the soon to be King Lepold I. He attempts to become the dominant power amongst the local systems by building up their battle fleet, and attacking the Foundation directly. Unfortunately, they have had to adopt the religion-of-science as a way to get working spaceships, which unwittingly places them in Hardin's power. Hardin has become effectively Head Priest of the religion. When Wienis takes him hostage on a visit, and attempts to take Terminus by force, Hardin diffuses the threat by using this religion against him, placing an interdict on the home planet of the Kingdom. Thus all technology on the planet and in the fleet is disabled and the destruction of the Foundation averted.

He is portrayed as a hero to The Foundation, and goes down as one of the most well-known characters in the series