In the autumn of the following year, some disputed claims, which his wife had on the estate of her maternal grandfather in Ireland, made it necessary for him to visit that country. Experience had painfully convinced him that theological controversy sometimes leads to personal animosity; and that few people were so open and direct in their mode of expressing hostility, as he himself was. Therefore, before going abroad, he took the precaution to ask letters from citizens of various classes and sects in Philadelphia; and he found no difficulty in obtaining them from the most respectable and distinguished. Matthew Carey, the well known philanthropist wrote as follows: "As you are about to visit my native country, and have applied to me for a testimonial concerning your character, I cheerfully comply with your request. I have been well acquainted with you for about thirty-five years, and I can testify that, during the whole of that time, you have been a perfect pest to our Southern neighbors. A Southern gentleman could scarcely visit this city, without having his slave taken from him by your instrumentality; so that they dread you, as they do the devil." After enjoying a mutual laugh over this epistle, another was written for the public, certifying that he had known Isaac T. Hopper for many years as "a useful and respectable citizen of the fairest character."

When Friend Hopper arrived in Ireland, he found many of the Quakers prejudiced against him, and many untrue stories in circulation, as he had expected. Sometimes, when he visited public places, he would overhear people saying to each other, in a low voice, "That's Isaac T. Hopper, who has given Friends so much trouble in America." A private letter from an "Orthodox" Quaker in Philadelphia was copied and circulated in all directions, greatly to his disadvantage. It represented him as a man of sanctified appearance, but wholly unworthy of credit; that business of a pecuniary nature was a mere pretence to cover artful designs; his real object being to spread heretical doctrines in Ireland, and thus sow dissension among Friends. In his journal of this visit to a foreign land, Friend Hopper says: "It is astonishing what strange ideas some of them have concerning me. They have been informed that I can find stolen goods, and am often applied to on such occasions. I think it would be no hard matter to make them believe me a wizard." This was probably a serious version of his pleasantry with the Dutchman about finding his goods by calculating the age of the moon.

Many of the Irish Friends had formed from hearsay the most extravagant misconceptions concerning the Friends called "Hicksites." They supposed them to be outright infidels, and that the grossest immoralities were tolerated among them; that they pointed loaded pistols at the "Orthodox" brethren, and drove them out of their own meeting-houses by main force. One of them expressed great surprise when Friend Hopper informed him that they were in the constant habit of reading the Scriptures in their families, and maintained among themselves the same discipline that had always been used in the Society. Sometimes when he attended Quaker meetings during the early portion of his visit, the ministers preached at him, by cautioning young people to beware of the adversary, who was now going about like a cunning serpent, in which form he was far more dangerous, than when he assumed the appearance of a roaring lion. But after a while, this tendency was rebuked by other preachers, who inculcated forbearance in judging others; reminding their hearers that the spirit of the Gospel always breathed peace and good will toward men. As for Isaac himself, he behaved with characteristic openness. When a stranger, in Quaker costume, introduced himself, and invited him to go home and dine with him, he replied, "I am represented by some people as a very bad man; and I do not wish to impose myself upon the hospitality of strangers, without letting them know who I am."

The stranger assured him that he knew very well who he was, and cared not a straw what opinions they accused him of; that he was going to have a company of Friends at dinner, who wished to converse with him. He went accordingly, and was received with true Irish hospitality and kindness.

Upon another occasion, a Quaker lady, who did not know he was a "Hicksite," observed to him, "I suppose the Society of Friends are very much thinned in America, since so many have gone off from them." He replied, "It is always best to be candid. I belong to the party called Hicksites, deists, and schismatics; and I suppose they are the ones to whom thou hast alluded as having gone off from the Society. I should like to talk with thee concerning the separation in America; for we have been greatly misrepresented. But I came to this country solely on business, and I have no wish to say or do anything that can unsettle the mind, or wound the feelings of any Friend." She seemed very much surprised, and for a minute or two covered her face with her hands. But when the company broke up, some hours after, she followed him into the entry, and cordially invited him to visit her. "What! canst thou tolerate the company of a heretic?" he exclaimed. She replied with a smile, "Yes, such a one as thou art."

In fact, wherever he had a chance to make himself known, prejudices melted away under the influence of his frank and kindly manners. Some people of other sects, as well of his own, took an interest in him for the very reasons that caused distrust and dislike in others; viz: because they had heard of him as the champion of perfect liberty of conscience, who considered it unnecessary to bind men by any creed whatsoever. Among these, he mentions in his journal, Professor Stokes of Dublin, who relinquished a salary of two thousand eight hundred pounds a year, because he could not conscientiously subscribe to the doctrine of the Trinity. It was proposed to dismiss him from the college altogether; but he demanded a hearing before the trustees and students. This privilege could not be denied, without infringing the laws of the institution; and deeming that such a discussion might prove injurious, they concluded to retain him, on a salary of eight hundred pounds. Friend Hopper describes him thus: "He is an intelligent and liberal-minded man, and has a faculty of exposing the errors and absurdities of the Athanasian Creed to much purpose. He was of a good spirit, and I was much gratified with his company. He insisted upon accompanying me home in the evening, and though I remonstrated against it, on account of his advanced age, he attended me to the door of my lodgings."

During this visit to Ireland, Friend Hopper was treated with great hospitality and respect by many who were wealthy, and many who were not wealthy; by members of the Society of Friends, and of various other religious sects. He formed a high estimate of the Irish character, and to the day of his death, always spoke with warm affection of the friends he found there. In his journal, he often alludes with pleasure to the children he met with, in families where he visited; for he was always extremely partial to the young. Speaking of a visit to a gentleman in the environs of Dublin, by the name of Wilson, he says: "I rose early in the morning, and the eldest daughter, about ten or eleven years old, very politely invited me to walk with her. We rambled about in the pastures, and through beautiful groves of oak, beech and holly. The little creature tried her very best to amuse me. She told me about the birds and the hares, and other inhabitants of the woods. She inquired whether I did not want very much to see my wife and children; and exclaimed, 'How I should like to see you meet them! It would give you so much pleasure!'" He speaks of a little girl in another family, who seemed very much attracted toward him, and finally whispered to her father, "I want to go and speak to that Friend." She was introduced accordingly, and they had much pleasant chat together.

In one of the families where he visited, they told him an instructive story concerning a Quaker who resided in Dublin, by the name of Joseph Torrey. One day when he was passing through the streets, he saw a man leading a horse, which was evidently much diseased. His compassionate heart was pained by the sight, and he asked the man where he was going. He replied, "The horse has the staggers, and I am going to sell him to the carrion-butchers."

"Wilt thou sell him to me for a crown!" inquired Joseph. The man readily assented, and the poor animal was led to the stable of his new friend, where he was most kindly tended. Suitable remedies and careful treatment soon restored him to health and beauty. One day, when Friend Torrey was riding him in Phoenix Park, a gentleman looked very earnestly at the horse, and at last inquired whether his owner would be willing to sell him. "Perhaps I would," replied Joseph, "if I could get a very good master for him."

"He so strongly resembles a favorite horse I once had, that I should think he was the same, if I didn't know he was dead," rejoined the stranger.