Terence McKenna pushed for the investigation of altered states of consciousness by the use of naturally occurring psychedelic chemicals, such as psychedelic mushrooms, ayahuasca, and DMT, which he considered to be the apotheosis of the psychedelic...
He also believed that the existence of other dimensions or worlds accessible in dreams or meditation could be inferred from how certain events are remembered. For example, he argued that since we cannot remember our lives before we were born, there is no way that our pre-natal memories could affect us after we are born, so these pre-natal memories must be stored in some sort of archive where they can be found when needed.
McKenna further proposed that this model of a vast internal memory system can be extended to include all living organisms, not just humans. He suggested that plants have a form of memory that allows them to adapt their behaviors to previous experiences with similar situations, while animals possess a more limited short-term memory but a larger long-term memory that allows them to learn from past mistakes.
As far as I know, Terence McKenna is the first person who has come up with this idea by himself. However, it has been discussed before by certain ancient philosophers including Parmenides and Plato. Parmenides was a Greek philosopher who lived around 515 BC, while Plato was an Athenian philosopher who lived between 427 and 347 BC.
Terence McKenna, who grew up in a ranching hamlet in Colorado, first encountered psychedelics in 1965, when he enrolled at the University of California, Berkeley to study ecology and shamanism (ah, the Sixties). While there, he became interested in drugs as a tool for understanding nature, and by 1971 he had changed his focus to psychology and psychiatry.
At the time, these were not popular subjects at Berkeley, so McKenna dropped out after one year. But he never lost interest in psychotropic plants, and during his time away from school he began to write about them. In 1973, he published an essay called "Drugs and the Future of Humanity," in which he argued that certain chemicals found in plants are capable of altering human consciousness in ways that improve rather than impair it. This convinced him to change his career path again, this time toward medicine.
So in 1974, at the age of twenty-one, he moved back home to work on a farm while trying to find a job in academia or medicine. However, due to the oil crisis of that era, there weren't many positions available, so he ended up working as a research assistant for $5,000 per year at the Mind/Brain Center at the University of California, Irvine.
Wundt was linked with structuralism, a theoretical viewpoint that focuses on defining the structures that make up the mind. He considered psychology to be the study of conscious experience, and he believed that trained observers could properly describe thoughts, sensations, and emotions through a process known as introspection. Through this method, they could identify certain mental processes as being similar to or different from physical processes by observing how each functioned in people who had brain damage. This approach is the basis for most modern theories of the mind.
Wundt proposed eight principles of psychological research that are still used today. These include the idea that knowledge grows through observation and experimentation, that every person has a unique personality, and that behavior can be explained by looking at the circumstances that trigger an action. He also suggested that psychologists should attempt to eliminate possible causes of observed phenomena before moving on to new studies. For example, if someone is experiencing pain, it is important not to startle them by banging on the door. Instead, you should check that nothing else is causing them discomfort before exploring other possibilities.
Wundt believed that the mind was made up of several separate functions that could be studied independently. These included perception, association, thought, feeling, will, and memory. He argued that the elements of our consciousness could be separated through careful observation and experimental testing, and this information could then be put back together to explain what happens when we think or feel something.