Final answer:
The absence of guilt for past actions may be explained by Kohlberg's stages of moral development, which suggests that an understanding of morality evolves through different stages, and philosophical perspectives like Socrates who believed wrongdoing stems from ignorance.
Step-by-step explanation:
The reason why someone may not feel any guilt for actions and thoughts could be complex and is often associated with their personal moral development and the influence of society. Kohlberg's stages of moral development shed light on why an individual's understanding of guilt and morality evolves over time. The progression from pre-conventional morality, which is self-centric, through conventional morality, where societal norms dictate behavior, to post-conventional morality, where universal principles of justice take precedence, can explain the internal shift in one's feelings of guilt or lack thereof.
In thinking of the philosophical perspective, individuals like Socrates view wrongdoing as a consequence of ignorance rather than a voluntary choice. If this line of thought is to be extended, then an individual's realization of their true nature or higher moral reasoning might elucidate why they never felt guilt before - because their actions and thoughts were in alignment with their understanding and principles at that time.