"The healthy stomach is nothing if it is not conservative. Few radicals have good digestions"

This quote by Samuel Butler is a metaphor for how one's mindset and outlook on life can impact their general wellbeing. The "healthy stomach" is a metaphor for a healthy mind and body, while the "conservative" attitude is a metaphor for a more moderate and well balanced technique to life. Butler is recommending that those who take a more severe and radical technique to life often suffer from bad mental and physical health. He is suggesting that a more moderate and balanced method to life is more beneficial for one's general wellbeing. This quote is a pointer to take a more moderate and well balanced method to life, instead of an extreme and radical one, in order to maintain good mental and physical health.