The objective of this work was to develop a comprehensive model of inner mental activity's trajectories. For this purpose, a review of updated research was conducted on the wandering mind topic - a phenomenon that has been recently conceptualized and that has become a focus of interest in cognitive sciences - alongside early psychological postulates on the inner speech phenomenon that were brought back to the surface of scientific literature. In summary, this article presents a reformulation of the spontaneous thought model by Andrews-Hanna et al. (2017), broadening its scope to approach inner mental activity in all its forms and transitions. It is concluded that modern cognitive research has overlooked the full complexity of different types and forms of consciousness' expressions, understanding them as isolated phenomena and sub-dimensioning their trajectories during the flow of experience. This, mainly, due to a scarce incorporation of temporality and morphology to current theoretical models. It is proposed that cognitive acts described in modern research (spontaneous, controlled, involuntary, etc.) are, in synthesis, different symbolic and expressive natures of inner mental activity or thought phenomenon, which current literature has failed to understand as a whole. This article constitutes a contribution to future theoretical and experimental research that seeks out to explore the nature of thought and its development during a cognitive act.