This quote suggests that quacks, or fraudulent practitioners (particularly in the field of medicine), are the biggest liars, except for their patients. The implication here is that these practitioners deceive people with false promises or unfounded treatments, but their patients, in turn, may also be deceiving themselves by choosing to believe in these false promises or treatments.

The deeper layer of this quote is a commentary on human nature and self-deception. People often want to believe in easy solutions to their problems, even when these solutions are not based on solid evidence or logic. This desire to believe can lead them to ignore the reality of their situation and accept the lies of quacks.

In today’s world, this idea is still very relevant. In the era of the internet and social media, misinformation can spread rapidly, and many people fall victim to various forms of deception, from fake news to scam products. People may choose to believe in these lies because they offer easy answers, comfort, or hope, even when these answers are not grounded in reality.

In terms of personal development, this quote serves as a reminder to always question and critically examine the information we receive, especially when it offers easy solutions to complex problems. It also underscores the importance of self-honesty. We must be willing to face the truth of our situations, no matter how difficult or uncomfortable, rather than deceiving ourselves with comforting lies. This can lead to more informed decisions, personal growth, and ultimately, a better understanding of ourselves and the world around us.