But since the world, which thou art to strive against, is not without thee, but within thee, it follows, that it is also to be conquered not without, but within thee.

His principal work Wahres Christentum (book 1: 1605; books 1-4: 1606-1610) i. At Wittenberg the crypto-Calvinist controversy was then at its height and he took the side of Melanchthon and the crypto-Calvinists. After Wahres Christentum Arndt's best-known work is Paradiesgärtlein aller christlichen Tugenden which was publiJohann Arndtd in 1612.

Johann Arndt (or Arnd; 27 December 1555 – 11 May 1621) was a German Lutheran theologian who wrote several influential books of devotional Christianity.