The "billiard ball" hypothesis, a product of Newtonian physics, argues that once the initial conditions of the universe have been established, the rest of the history of the universe follows inevitably. If it were actually possible to have complete knowledge of physical matter and all of the laws governing that matter at any one time, then it would be theoretically possible to compute the time and place of every event that will ever occur (Laplaces demon). In this sense, the basic particles of the universe operate in the same fashion as the rolling balls on a billiard table, moving and striking each other in predictable ways to produce predictable results. Whether or not it is all-encompassing in so doing, Newtonian mechanics deals only with caused events; for example, if an object begins in a known position and is hit dead on by an object with some known velocity, then it will be pushed straight toward another predictable point. If it goes somewhere else, the Newtonians argue, one must question ones measurements of the original position of the object, the exact direction of the striking object, gravitational or other fields that were inadvertently ignored, etc. Then, they maintain, repeated experiments and improvements in accuracy will always bring ones observations closer to the theoretically predicted results. When dealing with situations on an ordinary human scale, Newtonian physics has been successful. But it fails as velocities become some substantial fraction of the speed of light and when interactions at the atomic scale are studied.
Additionally, tumors and kidney stones can block the urethra. Spinal cord injuries or nervous system disorders are additional causes of overflow incontinence. In men, benign prostatic hyperplasia (BPH) may also restrict the flow of urine. Overflow incontinence is rare in women, although sometimes it is caused by fibroid or ovarian tumors. Also overflow incontinence can be from increased outlet resistance from advanced vaginal prolapse causing a "kink" in the urethra or after an anti-incontinence procedure which has overcorrected the problem. Early symptoms include a hesitant or slow stream of urine during voluntary urination. Anticholinergic and NSAIDs medications may worsen overflow incontinence. Criticism
The concept of overflow incontinence has been criticised, because it is difficult to define and because the definitions that have been proposed have little clinical significance. The concept is a purely theoretical one that is not based on evidence. Overflow incontinence cannot be measured and can therefore not be reliably diagnosed. In the urological literature and in medical care the concept is therefore of little importance, with the related concept of chronic urinary retention being the much more relevant and useful one.In 2017 the Quality Improvement and Patient Safety (QIPS) committee of the American Urological Association (AUA) published a definition of nonneurogenic chronic urinary retention as a post-void residual of greater than 300 mL that was measured at least twice and extended over a period at least six months. Measurement of post-void residual by medical ultrasound is an easy procedure that is sufficient in most cases.