In any case, the key difference between Buddhism and non-Buddhism lies in taking refuge in the Three Jewels.

Accordingly, taking refuge is deemed a prerequisite for anyone who wants to learn Buddhism. However, it has never been forced upon anyone. Only those who want to learn the Buddha’s teachings or take up Buddhist practice must satisfy this requirement. Not taking refuge is to remain an “outsider,” off the path to liberation, and one cannot be deemed a Buddhist.

[Depicted from Luminous Wisdom Book Series 1 : The Right View ~ The Three Differences]