Wickliffe was afterward elected to the chair of the divinity professor: and now fully convinced of the errors of the Romish church, and the vileness of its monastic agents, he determined to expose them. In public lectures he lashed their vices and opposed their follies. He unfolded a variety of abuses covered by the darkness of superstition. At first he began to loosen the prejudices of the vulgar, and proceeded by slow advances; with the metaphysical disquisitions of the age, he mingled opinions in divinity apparently novel. The usurpations of the court of Rome was a favourite topic. On these he expatiated with all the keenness of argument, joined to logical reasoning. This soon procured him the clamour of the clergy, who, with the archbishop of Canterbury, deprived him of his office.

At this time, the administration of affairs was in the hands of the duke of Lancaster, well known by the name of John of Gaunt. This prince had very free notions of religion, and was at enmity with the clergy. The exactions of the court of Rome having become very burdensome, he determined to send the bishop of Bangor and Wickliffe to remonstrate against these abuses, and it was agreed that the pope should no longer dispose of any benifices belonging to the church of England. In this embassy, Wickliffe's observant mind penetrated into the constitution and policy of Rome, and he returned more strongly than ever determined to expose its avarice and ambition.

Having recovered his former situation, he inveighed, in his lectures, against the pope—his usurpation—his infallibility—his pride—his avarice—and his tyranny. He was the first who termed the pope Antichrist. From the pope, he would turn to the pomp, the luxury and trappings of the bishops, and compared them with the simplicity of primitive bishops. Their superstitions and deceptions were topics that he urged with energy of mind and logical precision.

From the patronage of the duke of Lancaster, Wickliffe received a good benefice; but he was no sooner settled in his parish, than his enemies and the bishops began to persecute him with renewed vigor. The duke of Lancaster was his friend in this persecution, and by his presence and that of Lord Percy, earl marshal of England, he so overawed the trial, that the whole ended in disorder.

After the death of Edward III. his grandson Richard II. succeeded, in the eleventh year of his age. The duke of Lancaster not obtaining to be the sole regent, as he expected, his power began to decline, and the enemies of Wickliffe, taking advantage of this circumstance, renewed their articles of accusation against him. Five bulls were despatched in consequence by the pope to the king and certain bishops, but the regency and the people manifested a spirit of contempt at the haughty proceedings of the pontiff, and the former at that time wanting money to oppose an expected invasion of the French, proposed to apply a large sum, collected for the use of the pope to that purpose. The question was submitted to the decision of Wickliffe. The bishops, however, supported by the papal authority, insisted upon bringing Wickliffe to trial, and he was actually undergoing examination at Lambeth, when, from the riotous behaviour of the populace without, and awed by the command of sir Lewis Clifford, a gentleman of the court, that they should not proceed to any definitive sentence, they terminated the whole affair in a prohibition to Wickliffe, not to preach those doctrines which were obnoxious to the pope; but this was laughed at by our reformer, who, going about barefoot, and in a long frieze gown, preached more vehemently than before.

In the year 1378, a contest arose between two popes, Urban VI. and Clement VII. which was the lawful pope, and true vicegerent of God. This was a favourable period for the exertion of Wickliffe's talents: he soon produced a tract against popery, which was eagerly read by all sorts of people.

About the end of the year, Wickliffe was seized with a violent disorder, which it was feared might prove fatal. The begging friars, accompanied by four of the most eminent citizens of Oxford, gained admittance to his bed-chamber, and begged of him to retract, for his soul's sake, the unjust things he had asserted of their order. Wickliffe surprised at the solemn message, raised himself in his bed, and with a stern countenance replied, "I shall not die, but live to declare the evil deeds of the friars."

When Wickliffe recovered, he set about a most important work, the translation of the bible into English. Before this work appeared, he published a tract, wherein he showed the necessity of it. The zeal of the bishops to suppress the scriptures, greatly promoted its sale, and they who were not able to purchase copies, procured transcripts of particular gospels or epistles. Afterward, when Lollardy increased, and the flames kindled, it was a common practice to fasten about the neck of the condemned heretic such of these scraps of scripture as were found in his possession, which generally shared his fate.

Immediately after this transaction, Wickliffe ventured a step further, and affected the doctrine of transubstantiation. This strange opinion was invented by Paschade Radbert, and asserted with amazing boldness. Wickliffe, in his lecture before the university of Oxford, 1381, attacked this doctrine, and published a treatise on the subject. Dr. Barton, at this time vice-chancellor of Oxford, calling together the heads of the university, condemned Wickliffe's doctrines as heretical, and threatened their author with excommunication. Wickliffe could now derive no support from the duke of Lancaster, and being cited to appear before his former adversary, William Courteney, now made archbishop of Canterbury, he sheltered himself under the plea, that, as a member of the university, he was exempt from episcopal jurisdiction. This plea was admitted, as the university were determined to support their member.

The court met at the appointed time, determined, at least to sit in judgment upon his opinions, and some they condemned as erroneous, others as heretical. The publication on this subject was immediately answered by Wickliffe, who had become a subject of the archbishop's determined malice. The king, solicited by the archbishop, granted a license to imprison the teacher of heresy, but the commons made the king revoke this act as illegal. The primate, however, obtained letters from the king, directing the head of the university of Oxford to search for all heresies and the books published by Wickliffe; in consequence of which order, the university became a scene of tumult. Wickliffe is supposed to have retired from the storm, into an obscure part of the kingdom. The seeds, however, were scattered, and Wickliffe's opinions were so prevalent, that it was said, if you met two persons upon the road, you might be sure that one was a Lollard. At this period, the disputes between the two popes continued. Urban published a bull, in which he earnestly called upon all who had any regard for religion, to exert themselves in its cause; and to take up arms against Clement and his adherents in defence of the holy see.