"There came at that time to Frankfort, for the purpose of enjoying the friendship and intercourse with the Rev. Dr. Spener, a noble lady, who had formerly been maid of honour at a court; and as I desired much to have, if only for once, some talk with her, I begged the reverend doctor to give me her address in a note. This he did, and I went to her, and presented her with my last disputation, under the impression that it would not be disagreeable to her, as she had learnt Hebrew and had much acquaintance with the Holy Scriptures. But she told me that I had therein glorified 'the god Petersen,' and that, for a true knowledge of God in Christ, far more was required than such worldly learning, which produced generally a boastful spirit, and whereby one could hardly attain to the godly simplicity of heavenly things. This speech sank deep into my heart, and I was at once convinced of the truth of it. After that I began to write a little book, wherein I noted down what I heard from pious people concerning the way to true godliness; and I began to practise what I had thus learnt, for without this effectual working all else would be fruitless. "Now when I had been strengthened in this course, I went back to Giessen, where the change in me was soon perceived; and they began to ridicule me on account of my 'piety.' But I cared little for it." (Petersen afterwards returned to his home, at Lubeck, and became there professor of poetry, but met with great enmity from the Jesuits. In 1677 he became preacher at Hanover; and was called from thence, in 1678, to Cutin, as the court preacher to the Duke of Holstein.)