Modern adult brain surgery is a very new discipline. While many would consider the fathers of modern neurosurgery to be people like Victor Horsley, Harvey Cushing, and Walter Dandy, they all worked in the early 20th century, in an era before the creation of equipment now considered to be “game-changers” in the field of neurosurgery. Only towards the end of the 20th century did we see such critical advances as the operating microscope, the wide availability of CT and MRI imaging, neuro-endoscopy, stereotactic neuro-navigation, stereotactic radiosurgery, interventional neuro-endovascular techniques, and intra-operative neuromonitoring. It is not just that these advances occurred only recently, but it is even more recently that they have become accessible to many neurosurgeons. Furthermore, the scientific evidence for adult brain surgery in this new era is itself extremely new and a work in progress. There is certainly both an “art” and a “science” to the practice of medicine andalso to the practice of adult brain surgery. Furthermore, there is also a wide range of acceptable practices in regards to adult brain surgery, ranging from the most conservative/minimally invasive options to the most aggressive approaches. The author of Put Down the Knife, neurosurgeon Dr. Michael Brisman, is of the belief that the pendulum in medicine has swung way too far to the “art” side and away from the “science.” Furthermore, given the very high risks associated with adult brain surgery, the default choice of treatment should be the more conservative/minimally invasive options when possible. This book explores adult brain surgery from a more conservative vantage point, highlighting potential errors in thought related to decision-making and rationales for brain surgery as well as interpretation of the surgical literature. Focused chapters then dive into considerations of less invasive and even non-invasive approaches for various conditions of the brain, including tumors,cysts, hematomas, pain and movement disorders, skull base disorders, and much more.