He was created a privy councillor in 1672, and, while it is believed that he was ignorant of the secret clauses in the Treaty of Dover, was chosen envoy to negotiate terms of peace with Louis XIV and the Dutch at Utrecht.

In 1674 he brought forward a motion for disarming "popish recusants," and supported one by Lord Carlisle for restricting the marriages in the royal family to Protestants; but he opposed the bill introduced by Lord Danby in 1675, that imposed a test oath on officials and members of parliament, speaking "with that quickness, learning and elegance that are inseparable from all his discourses," and ridiculing the multiplication of oaths, since "no man would ever sleep with open doors.

[7] In 1678 he took an active part in the investigation of the "Popish Plot," to which he appears to have given excessive credence, but opposed the bill that was passed on 30 October 1678, to exclude Roman Catholics from the House of Lords.

With Charles, who had at first "kicked at his appointment," he quickly became a favourite, his lively and "libertine" conversation being named by Bishop Gilbert Burnet as his chief attraction for the king.

According to Sir William Temple he showed great severity in putting the laws against the Roman Catholics into force although in 1680 he voted against the execution of Lord Stafford.

The debate that followed, one of the most famous in the annals of parliament, became a duel of oratory between Halifax and his uncle Shaftesbury, the finest two speakers of the day, watched by the Lords, the Commons at the bar, and the king, who was present.

His conduct transformed the allegiance to him of the Whigs into bitter hostility, the Commons immediately petitioning the king to remove him from his councils for ever, while any favour which he might have regained with James was forfeited by his subsequent approval of the regency scheme.

Halifax retired to Rufford again in January 1681, but was present at the Oxford Parliament, and in May returned suddenly to public life and held for a year the chief control of affairs.

Shaftesbury's arrest on 2 July was attributed to his influence, but in general, during the period of Tory reaction, he seems to have urged a policy of conciliation and moderation to the king.

He opposed James's return from Scotland and, about this time (September), made a characteristic but futile attempt to persuade the Duke to attend the services of the Church of England and thus to end all difficulties.

The influence of Halifax procured for the Dutch a formal assurance from Charles of his support; but the king informed the French ambassador that he had no intention of fulfilling his engagements, and made another secret treaty with Louis.

In 1682, Halifax opposed James's prosecution of the Earl of Argyll, arousing further hostility in the duke, while the same year he was challenged to a duel by Monmouth, who attributed to him his disgrace.

The Rye House Plot, in which it was sought to implicate them, was a disastrous blow to his policy, and in order to counteract its consequences he entered into somewhat perilous negotiations with Monmouth, and endeavoured to effect his reconciliation with the king.

In a debate in the cabinet of November 1684, on the question of the grant of a fresh constitution to the New England colonies, he urged with great warmth "that there could be no doubt whatever but that the same laws which are in force in England should also be established in a country inhabited by Englishmen and that an absolute government is neither so happy nor so safe as that which is tempered by laws and which sets bounds to the authority of the prince," and declared that he could not "live under a king who should have it in his power to take, whenever he thought proper, the money he has in his pocket."

Finally, on his firm refusal to support the repeal of the Test and Habeas Corpus Acts, he was dismissed, and his name was struck out of the list of the privy council.

In 1687 he published the famous Letter to a Dissenter, in which he warns the Nonconformists against being beguiled by the "Indulgence" into joining the court party, sets in a clear light the fatal results of such a step, and reminds them that under their next sovereign their grievances would in all probability be satisfied by the law.

He took the popular side on the occasion of the trial of the Seven Bishops in June 1688, visited them in the Tower, and led the cheers with which the verdict of "not guilty" was received in court; but the same month he refrained from signing the Invitation to William, and publicly repudiated any share in the prince's plans.

The moderate and comprehensive character of the settlement at the revolution plainly shows his guiding hand, and it was finally through his persuasion that the Lords yielded to the Commons and agreed to the compromise whereby William and Mary were declared joint sovereigns.

He thoroughly approved also at first of William's foreign policy; but, having excited the hostility of both the Whig and Tory parties, he now became exposed to a series of attacks in parliament which finally drove him from power.

He entered bail for Lord Marlborough when he was accused of complicity in a Jacobite plot in May 1692, and in June, during the absence of the king from England, his name was struck off the privy council.

His intellectual powers, his high character, his urbanity, vivacity and satirical humour made a great impression on his contemporaries, and many of his witty sayings have been recorded.

Maintaining throughout his career a detachment from party, he never acted permanently or continuously with either of the two great factions, and exasperated both in turn by deserting their cause at the moment when their hopes seemed on the point of realisation.

But the principle which chiefly influenced his political action, that of compromise, differed essentially from those of both parties, and his attitude with regard to the Whigs or Tories was thus by necessity continually changing.

For that view of his character which while allowing him the merit of a brilliant political theorist denies him the qualities of a man of action and of a practical politician, there is no solid basis.

The truth is that while his political ideas are founded upon great moral or philosophical generalisations, often vividly recalling and sometimes anticipating the broad conceptions of Edmund Burke, they are at the same time imbued with precisely those practical qualities which have ever been characteristic of English statesmenship, and were always capable of application to actual conditions.

He had no taste for abstract political dogma, but seemed to venture no further than to think that "men should live in some competent state of freedom," and that the limited monarchical and aristocratic government was the best adapted for his country.

The constant tendency of his mind towards antithesis and the balancing of opinions did not lead to paralysis in time of action – he did not shrink from responsibility, nor show on any occasion lack of courage.

Detested by the Whigs and by the Tories alike, and defended by neither, the favour alone of the king and his own transcendent abilities proved insufficient to withstand the constant and violent attacks made upon him in parliament, and he yielded to the superior force.

"His heart," says Burnet, "was much set on raising his family" — his last concern even while on his deathbed was the remarriage of his son Lord Elland to perpetuate his name; and this is probably the cause of his acceptance of so many titles for which he himself affected a philosophical indifference.

In The Anatomy of an Equivalent (1688) he treats with keen wit and power of analysis the proposal to grant a "perpetual edict" in favour of the Established Church in return for the repeal of the test and penal laws.