Buddhist texts don't describe rebirth as chosen; difficult rebirths result automatically from past karma, though some traditions describe bodhisattvas deliberately taking difficult births to help others.
In Buddhist cosmology, rebirth isn't typically a conscious choice. The Pali Canon describes rebirth as an automatic process driven by karma—actions from the past that create conditions for future existence. The specific circumstances of rebirth occur through a process sometimes called "karmic momentum." When a being dies, their accumulated karma determines the nature of their next birth, much like a ball rolling downhill finds its own level based on the terrain.
The Buddha taught that beings are "heir to their actions" (Dhammapada 165). Difficult circumstances arise because past actions have created conditions that naturally produce suffering in return. This isn't punishment from a judge but rather the inevitable structure of cause and effect. A person with deep delusion, greed, or hatred accrues karma that naturally leads to difficult rebirth conditions.
The question assumes that beings somehow evaluate their situation and choose difficult rebirths, which would be irrational. This confusion often arises from misunderstanding how karma operates. There is no decision-making process involved in karmic rebirth—at least not in the classical Theravada understanding found in the Pali texts. The process is automatic and mechanical, governed by the nature of past actions rather than by present consent.
Some confusion also comes from conflating different Buddhist concepts. The idea that a being "chooses" anything presupposes the existence of a stable, choosing "self" with continuity between lives. Yet Buddhist teaching on anatta (non-self) explicitly denies such a persistent ego that could make rebirth decisions.
Mahayana Buddhism introduces a different framework through the bodhisattva path. In texts like the Lotus Sutra, bodhisattvas are described as deliberately taking difficult rebirths to help suffering beings. A bodhisattva might be reborn in a hellish realm or as an animal specifically to alleviate suffering and guide beings toward enlightenment.
This represents a genuine choice, but it's explicitly a choice made by enlightened or highly advanced beings who can exercise conscious control over their rebirth. It's not applicable to ordinary sentient beings trapped in samsara. The bodhisattva's decision reflects their profound wisdom and compassion, operating from a place of liberation rather than from ignorance-driven karma.
The difficult circumstances of a birth exist because they're the appropriate result of past actions. Someone born into poverty, illness, or persecution has karma that corresponds to those conditions. This might result from past lifetimes of greed, harming others, or creating suffering, but the person being reborn doesn't consciously select these conditions—they simply manifest as consequences.
It's worth noting that even within a difficult birth, beings retain some agency in how they respond. A child born into hardship can still develop wisdom, compassion, and virtue through their choices in this life, thereby creating new karma that shapes future circumstances. The Pali texts describe this as "volitional action" (cetana), the intentional choices that create karma going forward.
Theravada Buddhism generally maintains the view described above: rebirth is automatic, determined by karma, not consciously chosen. Mahayana Buddhism allows for the bodhisattva exception while maintaining the same basic principle for ordinary beings. Some Tibetan Buddhist schools discuss subtle ways consciousness might influence rebirth circumstances, but again, this applies primarily to practitioners with advanced realization.
Tibetan Buddhism's bardo teachings, found in texts like the Tibetan Book of the Dead, describe intermediate states where consciousness might exert some influence, but this remains a complex philosophical territory with varying interpretations across schools. The fundamental principle—that difficult rebirths result from past karma—remains constant across traditions.
Understanding rebirth this way has a crucial philosophical function: it explains suffering and inequality without requiring belief in divine punishment or injustice. Everyone's circumstances arise from their own past actions, creating a system of responsibility and potential transformation. No one is randomly assigned suffering; it reflects a causal pattern that individuals can eventually alter through ethical action and wisdom.
This perspective also emphasizes that while circumstances are determined by karma, they're never permanent or deserved as moral judgment. A being in difficult circumstances can practice the path, develop wisdom, and through their own effort, generate karma that leads to better conditions in future lives or to liberation itself.