Consciousness has long been a focus of philosophical inquiry. Philosophers have employed thoughts supported by language and logic as a primary tool to examine the essence and structure of consciousness in mostly adult humans. Language elevates the abstraction of thought and has significantly contributed to the advancement of civilization. Within an individual, language plays a significant role to advance complexity in thought processes and provide richness to a variety of conscious experience. In this sense, modern philosophical research on consciousness is largely based on abstract thinking. Among the many critical thoughts, one of the most fundamental is Descartes’ famous dictum “Cogito ergo sum” (“I think, therefore I am”). From a viewpoint of consciousness, this implies “I cannot doubt the presence of my own consciousness.” Since Descartes, philosophical research on consciousness remained primarily dependent on logical and linguistic reasoning, while recent philosophers (especially after the 1990s, the second generation) started to incorporate neuroscientific insights into their thesis.