The theory was criticised for being circular; it used its own conclusion as evidence, offering no new explanatory power.

circular 来自名词 circle（圆圈），加上形容词后缀 -ar 构成，字面意思是"圆形的"。在逻辑论证中，circular 特指"循环的、自我循环的"，即用结论本身来证明结论，没有实质性的论证过程。