In 1792 the two brothers visited Paris, and this excursion seems to have formed the turning point of their lives and fortunes.  The French Revolution was in full swing, and in the society of Roland, Brissot, and other Republican leaders, the young Irishmen imbibed the love of freedom, and impatience of tyranny and oppression, which they clung to so faithfully, and which distinguished them so remarkably during the remainder of their lives.  On returning to Ireland in January, 1793, the brothers joined the ranks of the United Irishmen.  John at once became a prominent member of the society, and his signature appears to several of the spirited and eloquent addresses by which the Dublin branch sought from time to time to arouse the ardour and stimulate the exertions of their compatriots.  The society of United Irishmen looked for nothing more at this period than a thorough measure of parliamentary reform, household suffrage being the leading feature in their programme; but when the tyranny of the government drove the leaguers into more violent and dangerous courses, when republican government and separation from England were inscribed on the banners of the society instead of electoral reform, and when the selfish and the wavering had shrunk aside, the Sheareses still remained true to the United Irishmen, and seemed to grow more zealous and energetic in the cause of their country according as the mists of perplexity and danger gathered around it.

To follow out the history of the Sheareses connection with the United Irishmen would be foreign to our intention and to the scope of this work.  The limits of our space oblige us to pass over the ground at a rapid pace, and we shall dismiss the period of the Sheareses’ lives comprised in the years between 1793 and 1798, by saying that during that period, while practising their profession with success, they devoted themselves with all the earnestness of their nature to the furtherance of the objects of the United Irishmen.  In March, 1798, the affairs of the organization became critical; the arrest of the Directory at Oliver Bond’s deprived the party of its best and most trusted leaders, besides placing in the hands of the government a mass of information relative to the plans and resources of the conspirators.  To fill the gap thus caused, John Sheares was soon appointed a member of the Directory, and he threw himself into the work with all the ardour and energy of his nature.  The fortunes of the society had assumed a desperate phase when John Sheares became its ruling spirit.  Tone was in France, O’Connor was in England, Russell, Emmet, and Fitzgerald were in prison.  But Sheares was not disheartened; he directed all his efforts towards bringing about the insurrection for which his countrymen had so long been preparing, and the 23rd of May, 1798, was fixed on by him for the outbreak.  He was after visiting Wexford and Kildare, and making arrangements in those counties for the rising, and was on the verge of starting for Cork on a similar mission, when the hand of treachery cut short his career, and the gates of Kilmainham prison opened to receive him.