Philosophers and psychologists have long tried to understand people′s irrational behaviour through concepts such as weakness of will, compulsion and addiction. The scientific basis of the project has been greatly enhanced by advances in cognitive psychology and neuroscience. However, some philosophers have also been critical of the more general conclusions drawn by the scientists. This is especially true when scientific researchers start making claims that go to philosophical issues, such as free will and responsibility. Conversely, some scientists have been critical of philosophical approaches for not understanding the results of recent research. I examined some of the recent history of scientific claims about addiction, and the rise of the claims from scientists to have shown that addiction is a brain disease and that addictive behaviour is compulsive. Given the well-confirmed evidence that addicts can modulate their behaviour in response to rewards, punishments and context, it is clear that according to normal definitions of compulsivity the behaviour of addicts is not typically compulsive, suggesting that neuroscientists are making an error in their interpretation of data. Since philosophers have expertise in making distinctions between different kinds of action and categorising them as free, weak-willed and compulsive, we will achieve a better interpretation of the neuroscience of addiction when taking this philosophical work into account. Conversely, given the status of science in the modern world, philosophers have to grapple with the latest neuroscientific discoveries and show the compatibility of their philosophical theories with the data for their approaches to maintain credibility.