Under the influence of the movement Back to Nature (Zuruck zur Natur) his studies took up more and more of his time. He resigned his position as teacher around 1905 and founded a recovery centre, his Lebensheim in Witzhelden. The patients took enthusiastically to this simple and natural lifestyle and were inspired by this New Doctrine (Neue Lehre). His wife, Mathilde, passed away in 1912 and the outbreak of the First World War brought an end to his successful enterprise. His children Fritz, Luise, Maria and Ernst were grown up by this time while the youngest, Hermann, was still at school. From then on Peter Johannes practised as a nature-healer and concentrated on the study of Iridology (Augendiagnose). He had already published a paper in 1901 on this subject and was the first German to employ this type of diagnosis. His greatest achievement was his book Die Augendiagnose which was published in 1925. This was an extensive and voluminous work in  which he showed that all organs and their diseases as well as the entire nervous system are reflected in the human eyes and this could possibly lead to the diagnosis of the causes of diseases.

Besides running his practice, Peter Johannes taught many students. He continued to develop Iridology further and remained well known to many natural healers until long after he died. He wrote several other books including Die Odopathie, Das kleine Rezeptbuch der Odopathie and finally Die Antlitz-diagnose which was lost during the Second World War. His contribution to the discipline of Iridology was acknowledged in 1925 by the Academy of Medicine in Washington, USA who awarded him the title of Doctor of Medicine. He was, however prevented by the Prussian Academy of Medicine from using the title openly.

In 1922 Peter Johannes married for the second time. His bride, Lina Ostmeier was a young (34) and capable masseuse and together they operated an efficient practice in Bischofswerda where their twins Siegfried and Hellmut were born.

Lina was especially successful in her practise but unfortunately the young mother died in December 1925. In 1926 Peter Johannes moved his practice from the Rheinland to Bad-Schandau in Sachsen where he continued with his practice on his own. He bought a huge house which he named “Villa Thiel”, spacious enough to accomodate not only the family but also all the participants in the Peter Johannes Thiel courses.

One of the courses in natural healing was given in Villa Thiel from 15 to 26 March 1926. At the end of this event his daughter Luise and Adolf Engel announced their engagement as shown in the group photo including the students and some family members.

The notes at the bottom  of the photo were written by the participants in the course and was kept in  a book by Peter Johannes Thiel which is now in the possession of his great-granddaughter, Silke Maria Müller. The last entry in this book was written in Klein-Zschachwitz (Dresden) on 6 October 1941 indicating that he continued giving these courses until shortly before his death.

In 1928, when the twin brothers were five years old, Peter Johannes married his third wife Martha. Due to very difficult working conditions he could not continue his practice for long and had to give up Bad-Schandau. He returned to Boppard am Rhein where the authorities and the medical profession made it very difficult for him to continue his profession as Naturartz. They moved in 1934 from Rheinland to Sachsen (for the second time) where they lived in his newly restored house in Zschachwitz near Dresden. The house was beautifully situated near the Elbe River almost directly opposite Pilnitz Castle. Peter Johannes died in this house on 20 May 1942 from a gastric disorder. His third wife, Martha, survived him by 4 years.

An interesting description of the nature and character of Peter Johannes Thiel was given to me by one of his grandchildren, Eva Maria Müller (born Thun). She was the daughter of Maria Thun (born Thiel), Peter Johannes’ third child. She supplied me with most of the information about the life of Peter Johannes Thiel and with the names and other information about his descendents. She described him as an idealist and romanticist but he was not an astute businessman. He was, however, definitely an exceptional personality, well loved and respected by his followers. He loved his children and taught them the Wonders of Nature and the names of medicinal plants. Through unforgettable stories he also informed them about German history. Although he loved his heimat near the Rhine he always felt himself Prussian in his thoughts and feelings. Unfortunately he never felt at home in Prussia as the Prussian authorities and medical profession made life very difficult for him.