Strategic Problem The problem of understanding human consciousness is one of the biggest challenges in philosophy. Recent theoretical developments have led to a clear distinction between two types of theories (first-order and higher-order). Here we capitalize on the opportunity that according to current popular interpretations, the two theories make different empirical predictions that are testable by the state-of-the-art methods of cognitive neuroscience. Therefore we try to distinguish between first-order and higher-order theories of consciousness, by conducting experiments on human subjects. Activities This is an exercise of adversarial collaboration; two of the investigators (Block & Lau) hold opposing views of consciousness. They design the experiments together, and make predictions before data collection such that we can genuinely let the results determine the issues, minimizing the role of post-hoc interpretations which have often been equivocal in previous studies. We will conduct 3 experiments, using TMS (trancranial magnetic stimulation), fMRI (functional magnetic resonance imaging), and MEG (magnetoencephalography). Outputs We expect to produce at least 3 reports of empirical results and 1 interdisciplinary review paper, to be published in high-profile, peer-reviewed, journals. Also we will write 2 general articles that are suitable for a wider public readership. Outcomes We expect to contribute meaningfully to the philosophical debate between different theories of consciousness, providing new insights that are currently missing. Potential Enduring Impacts This research will contribute to a convincing resolution of some of the most perplexing problems in philosophy. This will be the first known attempt for a philosopher to take the initiative to collaborate with a scientists who hold an opposing view, and together try to empirically address the problem of consciousness. We hope this will set an example for future research.