Roughly speaking, Buddhism bases itself on the Four Noble Truths and the Eightfold Path. The Four Noble Truths are: There is suffering. There is a cause of suffering. There is an end to suffering. There is a way to end suffering.
The Eightfold Path consists of: Right View, Right Intention, Right Speech, Right Action, Right Livelihood, Right Effort, Right Mindfulness, and Right Concentration. The word "right" is sometimes translated as "complete" in order to create a wider context than a right-wrong dichotomy. The Eightfold Path offers the suggested steps anyone might take as they pursue a way to end suffering.
Today it occurred to me: Suppose that a dedicated and practicing Buddhist visited his or her favorite Buddhist temple or center. And suppose that after an hour or two of meditation or chanting or bowing or whatever prescribed ritual, s/he walked out the front door of the temple with the intent of going home. And suppose, on that walk home, all of a sudden, every jot and tittle of "Buddhism" were erased from his or her mind. Gone ... just gone ... all of it...a major brain fart ... a catastrophic Alzheimer's moment.
Buddhism ... all gone and there was no recollection of having forgotten anything.
Would the truth of suffering be any the less true? Perhaps it would be more true? In either case, Buddhism or no Buddhism, suffering does not take a holiday or rely on any -ism whatsoever.
Sometimes I am happy to call myself a Buddhist. :)
Buddhism is the forget-me-not of persuasions precisely because you can forget everything you ever learned or thought or concocted about it and it would still be true ... perhaps even true-r.
No one needs Buddhism in order to be a Buddhist.