This section is from the book "A Compend Of The Principles Of Homoeopathy", by William Boericke. Also available from Amazon: A Compend of the Principles of Homoeopathy as Taught by Hahnemann.
His researches and reflections, Hahnemann tells us in his work, led him to the conclusion that the cause of the constant recurrence of chronic diseases after their apparent or partial removal by the homoeopathic remedy, and their recurrence with new and grave symptoms, was that the symptoms manifesting themselves at any one time were only a portion of the deeply-seated fundamental malady, whose great extent was shown by the new symptoms that appeared from time to time. He believed it to be a chronic miasm, which the body could not throw off spontaneously and unaided, not by careful diet or regimen, but that it rather increased in intensity and extent from year to year.
"The most robust constitution, the best regulated life, and the greatest energy of the vital powers, are insufficient to extinguish them". § 78, Organon.