Circular? For this to be believed, please show a Sutta that shows the first element of paticcasamuppada arising in dependence upon final element of the paticcasamuppada.
In the absence of such a Sutta it would appear that the causes of avijja are actually a "not knowing" of the Four Noble Truths, fuelled by sensual desire, being and ignorance itself.
Metta,MN9 wrote:And what is ignorance, what is the origin of ignorance, what is the cessation of ignorance, what is the way leading to the cessation of ignorance? Not knowing about dukkha, not knowing about the origin of dukkha, not knowing about the cessation of dukkha, not knowing about the way leading to the cessation of dukkha — this is called ignorance. With the arising of the taints there is the arising of ignorance; with the cessation of the taints there is the cessation of ignorance. The way leading to the cessation of ignorance is just this Noble Eightfold Path; that is, right view... right concentration."
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"And what are the taints, what is the origin of the taints, what is the cessation of the taints, what is the way leading to the cessation of the taints? There are three taints: the taint of sensual desire, the taint of being and the taint of ignorance.
Paul.