This is the first edition collected tweets of Mark B. Reid, MD, @medicalaxioms. This project began in 2010 as place to share pithy quotes from famous old dead doctors. After running out of good content, I was forced to start making my own. Through the last 7 years, we’ve engaged in a jolly dialogue on the social media on topics ranging from common diagnostic mistakes to why it’s good for a doctor to have a dog. While all the content is mine, it’s richness comes as a result of the exchange between me and many other smart medical types on social media. This collection offers an inside look at medical education for students and residents and the observations of a doctor in practice for 20+ years. The statements within are not medical advice and should not be used to practice medicine, make medical decisions, or judge physicians or other healthcare workers. No axiom is true in all circumstances. Medicine is by it’s very nature non-binary-there is seldom one right answer for a given situation. The treatment that is good for one patient may easily kill another. Thus the practice of medicine should be left to trained experts who combine book learning, current medical literature, years of supervised training and personal experience to engage in a complicated but maximally effective practice based on medical judgment. It is far easier to judge a single medical decision than to practice good medicine, day in and day out, for years. As you read you will find contradictory statements-sometimes two aphorism directly oppose one another. This is the practice of medicine. We must sometimes hold two contradictory statements in the mind at the same time, hanging on to two competing hypotheses until one or the other becomes more correct. I hope you enjoy these aphorisms but if you find one you don’t like or you think you could write better, by all means do so! The instructions are contained within to send me edits and your own aphorisms. It’s my intention that reading this book would be an active, not passive, process. It should get you thinking about the rules you use in your practice and their exceptions. I hope it makes you think about how you were taught and what you learned and how you teach others. It is intended to be interactive and I hope you don’t agree with everything you read. There is much more style than evidence in a day of seeing patients.