Final answer:
Siddhartha sees the inadequacies in the Samanas' beliefs as their extreme asceticism does not address the true cause of suffering and is itself a form of attachment. Their practices conflict with the Buddha's teachings on the Four Noble Truths and the middle way, which advocate for a balanced approach to overcoming desire and suffering.
Step-by-step explanation:
Siddhartha, in Hermann Hesse's novel, perceives several inadequacies in the Samanas' beliefs and practices. His main contention concerns their approach to achieving enlightenment.
Siddhartha finds that the extreme asceticism and self-denial practiced by the Samanas do not truly lead to a higher understanding or liberation from suffering, which is the core goal of their practices. Siddhartha feels that the Samanas' lifestyle only perpetuates the cycle of suffering and does not address the root causes as defined by the Buddha's teachings.
Moreover, Siddhartha finds that the practice of self-mortification does not bring about the knowledge or experience necessary to achieve what the middle way recommends – a balanced approach to life without extreme indulgence or extreme deprivation.
It is this realization that propels Siddhartha on his journey to seek a more authentic path to enlightenment, ultimately discovering that true knowledge and peace come from experiencing the world fully and learning from it, rather than withdrawing from it.