By Silvia Polivoy

The human being shows a remarkable disposition to seek spiritual transcendence. Since the irrational cannot be erased from the human mind, the harder we try to deny it, the greater the power it will exert upon us. The spiritual experiences are associated to the occurrence of altered states of consciousness.
The society we live in considers (as opposed to shamanic knowledge) modified states of consciousness to be onanistic and vicious. Shamans argue that to satisfy our religious drive we have to experience the divine, and in order to achieve that, they use sacred plants. That is why the sacred plants are called entheogens, because they help experience the divine. 
Abraham Maslow called these experiences «peak experiences», but they are not limited to the altered states achieved through drugs or sacred plants. They can take place during meditation, hyperventilation, the practice of yoga, hypnosis, fast, physical suffering (such as the self-inflicted pain some saints underwent or the postures certain yoguis kept for months, etc). In short, it is a state that can be reached in many ways and, once there, we can explore aspects of reality which are different from those perceived in an ordinary state of consciousness. These different aspects of reality are well studied.
The orthodox branch of science considers these altered states subjective, therefore worthless. Then, these feelings of ecstasy, these other «dimensions» of reality, these occurrences of mystical reunion, of beauty, this crossing of the space-time barrier, can be catalogued as pathological. Traditional Psychiatry does not separate mysticism from psychosis. That is why Transpersonal Psychology blends science with the study of the spiritual capabilities of man using methods to alter the state of consciousness, because the spiritual phenomena seem to be incomprehensible in an ordinary state of consciousness.

Modified states of consciousness may have a dangerous side because, since they affect the defense mechanisms of the individual, they may pave the way for unacceptable, repressed material from the individual’s past to the conscious mind and cause restlessness, which could rise to terrifying levels if the individual is unable to cope with his anxiety (this is what is usually known as a «bad trip»). That is why previous psychological counseling is advised, for the individual to be able to tell what comes from the outside from what comes from the inside. It is recommended, also, to experience such modified states of consciousness in the context of psychotherapy, under the supervision of qualified, well trained professionals.
But, in spite of the risks, the spiritual experiences, the unconscious material, and the altered amplified of consciousness related to them, are too valuable to be ignored. Thus psychotherapy takes advantage of the information, available when the repression mechanism is weak, to modify unwanted patterns of behaviour.
Most psychoactive substances resemble (and sometimes are identical to) substances normally produced by the human body. Therefore, the individual has a built-in capacity to experiment psychedelic states, which are inherent to certain aspects of the human mind inaccessible during wakefulness. So, under the appropriate circumstances, these substances allow the individual (for a limited period of time) to gain access to deeper parts of his psyche.
Through dreams we get in touch with those aspects of our personality which are hidden from the conscious mind. The entheogenic or psychointegrative plants help reach those states that we experience while dreaming or while in the middle of those rare, ecstatic epiphanies that can happen while we are awake. Unlike most drugs, entheogenic plants do not produce physical dependence. A quick, time-limited tolerance (that does not increase with the dose administered) is also characteristic.
Their main use is to spot the individual’s conditionings and destroy them, to be unselfish by dissolving momentarily the limits of the ego, to expand the inner vision, to be more lucid, obtaining in that fashion very important insights. In short, to be able to recognize the forces, the impulses behind the individual’s actions and emotions, to track thoughts back to their source and to be in control of one’s life. That’s why they help the individual to become one.
Due to all this the sacred plants are called psychointegrative, or entheogenic. The list includes Ayahuasca, Peyote, Psilocybin mushrooms, Salvia divinorum, San Pedro (a cactus), Epena, Cebil, Brugmansia, among others.
Abraham Maslow in his book called «The psychology of Science» has shown how science might be the best neurotic defense mechanism invented by man, because the selective rejection wielded by human knowledge acts as a defense and therefore constitutes a neurotic maneuver which, out of fear, disqualifies transpersonal experiences as objects of study.
We’d all benefit if science became an open sistem oriented to personal growth.
Modern physics teaches us about the Universe’s unity, in which consciousness plays a role much closer to the one described by the great mystics.
When we transcend the ego for however brief, it is the beginning of an awakening to our true Self.