Psychedelics, in medical terms, is an inexact category of drugs that affect perceptions and cognition. Their proponents say 1960s-era associations have undermined exciting research in the field of neuroscience. Psychedelics should be made much more widely available, they contend, to treat a range of mental and emotional issues, as well as to ascertain a more profound sense of ourselves. People should also be empowered to make their own decisions in its use. Not so fast, say opponents. These are powerful substances.