His rapid proficiency in legal studies not only justified and confirmed the good opinion which had been formed of him by his early friend and patron, Serjeant Glanville, but also introduced him to the favourable notice of several of the most distinguished lawyers of that day. Noy, the Attorney-General, who some years afterwards devised the odious scheme of ship-money, and who, while he is called by Lord Clarendon “a morose and proud man,” is also represented by him as an “able and learned lawyer,” took particular notice of Hale, and advised and assisted him in his studies. At this time also he became intimate with Selden, who, though much older than himself, honoured him with his patronage and friendship. He was induced by the advice and example of this great man to extend his reading beyond the contracted sphere of his professional studies, to enlarge and strengthen his reasoning powers by philosophical inquiries, and to store his mind with a variety of general knowledge. The variety of his pursuits at this period of life was remarkable: anatomy, physiology, and divinity formed part only of his extensive course of reading; and by his subsequent writings it is made manifest that his knowledge of these subjects was by no means superficial.

The exact period at which Hale was called to the bar is not given by any of his biographers; and in consequence of the non-arrangement of the earlier records at Lincoln’s Inn, it cannot be readily ascertained. It is probable however that he commenced the actual practice of his profession about the year 1636. It is plain that he very soon attained considerable reputation in it, from his having been employed in most of the celebrated trials arising out of the troubles consequent on the meeting of Parliament in 1640. His prudence and political moderation, together with his great legal and constitutional knowledge, pointed him out as a valuable advocate for such of the court party as were brought to public trial. Bishop Burnet says that he was assigned as counsel for Lord Strafford, in 1640. This does not appear from the reports of that trial, nor is it on record that he was expressly assigned as Strafford’s counsel by the House of Lords: but he may have been privately retained by that nobleman to assist in preparing his defence. In 1643 however he was expressly appointed by both Houses of Parliament as counsel for Archbishop Laud: and the argument of Mr. Herne, the senior counsel, an elaborate and lucid piece of legal reasoning, is said, but on no certain authority, to have been drawn up by Hale. In 1647 he was appointed one of the counsel for the Eleven members: and he is said to have been afterwards retained for the defence of Charles I. in the High Court of Justice: but as the King refused to own the jurisdiction of the tribunal, his counsel took no public part in the proceedings. He was also retained after the King’s death by the Duke of Hamilton, when brought to trial for treason, in taking up arms against the Parliament. Burnet mentions other instances, but these are enough to prove his high reputation for fidelity and courage, as well as learning.

In the year 1643 Hale took the covenant as prescribed by the Parliament, and appeared more than once with other laymen in the assembly of divines. In 1651 he took the “Engagement to be faithful and true to the Commonwealth without a King and House of Lords,” which, as Mr. Justice Foster observes, “in the sense of those who imposed it, was plainly an engagement for abolishing kingly government, or at least for supporting the abolition of it.” In consequence of his compliance in this respect he was allowed to practise at the bar, and was shortly afterwards appointed a member of the commission for considering of the reformation of the law. The precise part taken by Hale in the deliberations of that body cannot now be ascertained; and indeed there are no records of the mode in which they conducted their inquiries, and, with a few exceptions, no details of the specific measures of reform introduced by them. A comparison, however, of the machinery of courts of justice during the reign of Charles I., and their practice and general conduct during the Commonwealth, and immediately after the Restoration, will afford convincing proofs that during the interregnum improvements of great importance were effected; improvements which must have been devised, matured, and carried into execution by minds of no common wisdom, devoted to the subject with extraordinary industry and reflection.

It was unquestionably with the view of restoring a respect for the administration of justice, which had been wholly lost during the reign of Charles I., and giving popularity and moral strength to his own government, that Cromwell determined to place such men as Hale on the benches of the different courts. Hale however had at first many scruples concerning the propriety of acting under a commission from an usurper; and it was not without much hesitation, that he at length yielded to the importunity of Cromwell and the urgent advice and entreaties of his friends; who, thinking it no small security to the nation to have a man of his integrity and high character on the bench, spared no pains to satisfy his conscientious scruples. He was made a serjeant, and raised to the bench of the Court of Common Pleas in January, 1653–4.

Soon after he became a judge he was returned to Cromwell’s first Parliament of five months, as one of the knights of the shire for the county of Gloucester, but he does not appear to have taken a very active part in the proceedings of that assembly. Burnet says that “he, with a great many others, came to parliaments, more out of a design to hinder mischief than to do much good.” On one occasion, however, he did a service to his country, for which all subsequent generations have reason to be grateful, by opposing the proposition of a party of frantic enthusiasts to destroy the records in the Tower and other depositories, as remnants of feudality and barbarism. Hale displayed the folly, injustice, and mischief of this proposition with such authority and clearness of argument, that he carried the opinions of all reasonable members with him; and in the end those who had introduced the measure were well satisfied to withdraw it. That his political opinions at this time were not republican, is evident from a motion introduced by him, that the legislative authority should be affirmed to be in the Parliament, and an individual with powers limited by the Parliament; but that the military power should for the present remain with the Protector. He had no seat in the second Parliament of the Protectorate, called in 1656; but when a new Parliament was summoned upon the death of Cromwell in January, 1658–9, he represented the University of Oxford.

His judicial conduct during the Commonwealth is represented by contemporaries of all parties as scrupulously just, and nobly independent. Several instances are related of his resolute refusal to submit the free administration of the law to the arbitrary dictation of the Protector. On one occasion of this kind, which occurred on the circuit, a jury had been packed by express directions from Cromwell. Hale discharged the jury on discovering this circumstance, and refused to try the cause. When he returned to London, the Protector severely reprimanded him, telling him that “he was not fit to be a judge;” to which Hale only replied that “it was very true.”

It appears that at this period, he, in common with several other judges, had strong objections to being employed by Cromwell as commissioners on the trial of persons taken in open resistance to his authority. After the suppression of the feeble and ineffectual rebellion in 1655, in which the unfortunate Colonel Penruddock, with many other gentlemen of rank and distinction, appeared in arms for the King in the western counties, a special commission issued for the trial of the offenders at Exeter, in which Hale’s name was inserted. He happened to be spending the Lent vacation at his house at Alderley, to which place an express was sent to require his attendance; but he plainly refused to go, excusing himself on the ground that four terms and two circuits in the year were a sufficient devotion of his time to his judicial duties, and that the intervals were already too small for the arrangement of his private affairs; “but,” says Burnet, “if he had been urged to it, he would not have been afraid of speaking more clearly.”

He continued to occupy his place as a judge of the Common Pleas until the death of the Protector; but when a new commission from Richard Cromwell was offered to him, he declined to receive it: and though strongly urged by other judges, as well as his personal friends, to accept the office on patriotic grounds, he firmly adhered to his first resolution, saying that “he could act no longer under such authority.”

In the year 1660 Hale was again returned by his native county of Gloucester to serve in the Parliament, or Convention, by which Charles II. was recalled. On the discussion of the means by which this event should be brought about, Hale proposed that a committee should be appointed to look into the propositions and concessions offered by Charles I. during the war, particularly at the treaty of Newport, from whence they might form reasonable conditions to be sent over to the King. The motion was successfully opposed by Monk, who urged the danger which might arise, in the present state of the army and the nation, if any delay should occur in the immediate settlement of the government. “This,” says Burnet, “was echoed with such a shout over the House, that the motion was no longer insisted on.” It can hardly be doubted that most of the destructive errors of the reign of Charles II. would have been spared, if express restrictions had been imposed upon him before he was permitted to assume the reins of government. On the other hand it has been justly said, that the time was critical; that at that precise moment the army and the nation, equally weary of the scenes of confusion and misrule which had succeeded to Richard Cromwell’s abdication, agreed upon the proposed scheme; but that if delay had been interposed, and if debates had arisen in Parliament, the dormant spirit of party would in all probability have been awakened, the opportunity would have been lost, and the restoration might after all have been prevented. These arguments, when urged by Monk to those who were suffering under a pressing evil, and had only a prospective and contingent danger before them, were plausible and convincing; but to those in after times who have marked the actual consequences of recalling the King without expressly limiting and defining his authority, as displayed in the miserable and disgraceful events of his “wicked, turbulent, and sanguinary reign,” and in the necessary occurrence of another revolution within thirty years from the Restoration, it will probably appear that our ancestors paid rather too dearly on that occasion for the advantages of an immediate settlement of the nation.

Immediately after the restoration of the King in May, 1668, Lord Clarendon, being appointed Lord Chancellor, sought to give strength and stability to the new government, by carefully providing for the due administration of justice. With this view, he placed men distinguished for their learning and high judicial character upon the benches of the different courts. Amongst other eminent lawyers, who had forsaken their profession during the latter period of the Commonwealth, he determined to recall Hale from his retirement, and offered him the appointment of Lord Chief Baron. But it was not without great difficulty that Hale was induced to return to the labours of public life. A curious original paper containing his “reasons why he desired to be spared from any place of public employment,” was published some years ago by Mr. Hargrave, in the preface to his collection of law tracts. Amongst these reasons, which were stated with the characteristic simplicity of this great man, he urged “the smallness of his estate, being not above £500 per annum, six children unprovided for, and a debt of £1000 lying upon him; that he was not so well able to endure travel and pains as formerly; that his constitution of body required some ease and relaxation; and that he had of late time declined the study of the law, and principally applied himself to other studies, now more easy, grateful, and seasonable for him.” He alludes also to two “infirmities, which make him unfit for that employment, first, an aversion to the pomp and grandeur necessarily incident to it; and secondly, too much pity, clemency, and tenderness in cases of life, which might prove an unserviceable temper.” “But if,” he concludes, “after all this, there must be a necessity of undertaking an employment, I desire that it may be in such a court and way as may be most suitable to my course of studies and education, and that it may be the lowest place that may be, to avoid envy. One of his Majesty’s counsel in ordinary, or at most, the place of a puisne judge in the Common Pleas, would suit me best.” His scruples were however eventually overcome, and on the 7th of November, 1660, he accepted the appointment of Lord Chief Baron: Lord Clarendon saying as he delivered his commission to him that “if the King could have found an honester and fitter man for that employment he would not have advanced him to it; and that he had therefore preferred him, because he knew no other who deserved it so well.” Shortly afterwards he reluctantly received the honour of knighthood.