The paper focuses on the science fiction novels Permutation City and Quarantine by Greg Egan and analyses his ideas on how life-altering technologies and life-simulating sciences are transforming human life, our consciousness, and our understanding of concepts, such as human/non-human, ecology, and the world around us. The paper studies the way Egan explores the themes of posthumanism, simulated realities, and digital immortality, through the prism of various ethical, social, philosophical, ecological and other problems that these concepts inevitably generate. The rich scientific background of these hard sf novels is analysed. The author also analyses Altered Carbon by Morgan, and compares it to the works of Greg Egan.