Sir Isaac Newton:
The Baptists are the only known body of Christians that has not symbolized with the Church of Rome.—The First Church, J. T. Mann

Mosheim (Lutheran):
Before the rise of Luther and Calvin, there lay secreted in almost all the countries of Europe persons who adhered tenaciously to the principles of modern Dutch Baptists.—The Baptist Spirit, Isaac J. Van Ness, William D. Nowlin

Cardinal Hosius (Catholic, 1524), President of the Council of Trent:
“Were it not that the Baptists have been grievously tormented and cut off with the knife during the past twelve hundred years, they would swarm in greater number than all the Reformers.”—Hosius, Letters, Apud Opera, p. 112, 113.

The “twelve hundred years” were the years preceding the Reformation in which Rome persecuted Baptists with the most cruel persecution thinkable.

Edinburg Cyclopedia (Presbyterian):
“It must have already occurred to our readers that the Baptists are the same sect of Christians that were formerly described as Ana-Baptists. Indeed this seems to have been their leading principle from the time of Tertullian to the present time.”—The Trail of Blood, J. M. Carroll

John Clark Ridpath (Methodist):
“I should not readily admit that there was a Baptist Church as far back as A. D. 100, though without doubt there were Baptists then, as all Christians were then Baptists.”—Cole C.D. Definitions of Doctrine, Volume III, The New Testament Church

Professor Wm. C. Duncan, of the Department of Greek and Latin, University of Louisiana:
“Baptists do not, as most Protestant denominations, date their origin from the Reformation of 1520. By means of that great movement they were brought out of comparative obscurity into prominent notice. They did not, however, originate with the Reformation; for long before Luther lived; yea, long before the Catholic Church itself was known, Baptist and Baptist churches flourished in Europe, Asia and Africa.”—Moser, M. L. Jr. Baptist Handbook for Church Members (Revised), Little Rock, Arkansas: Challenge Press, 1983, p. 46.

Zwingli, the the Swiss reformer, contemporary with Luther and Calvin (1525):
“The institution of Anabaptism is no novelty but for thirteen hundred years has caused great disturbances in the church and has acquired such a strength that the attempt in this age to contend with it appeared futile for a while.”—Dayton, Amos Cooper. Pedobaptist and Campbellite Immersions. Southwestern Publishing House, 1858, p. 150. (By the “church” Zwingli means the Roman Catholic church.)

Robert Barclay (Quaker):
“We shall afterwards show the rise of the Anabaptists took place prior to the Reformation of the Church of England, and there are also reasons for believing that on the Continent of Europe small hidden Christian societies, who have held many of the opinions of the Anabaptists, have existed from the times of the apostles.”—Christian, John T. History of the Baptists together with Some Account of Their Principles and Practices. Nashville, TN: Baptist Sunday School Committee of the American Baptist Association, 1922

William C. King
“Of the Baptists it may be said that they are not Reformers. These people, comprising bodies of Christian believers, known under various names in different countries, are entirely independent of and distinct from the Greek and Roman churches, and have an unbroken continuity from apostolic days down through the centuries. Throughout this long period they were bitterly persecuted for heresy, driven from country to country, disfranchised, deprived of their property, imprisoned, tortured and slain by the thousands; yet they swerved not from the New Testament faith, doctrine and practice.”—King, William C. Crossing the Centuries. Springfield, MA: Editorial Associates, 1912