 Care must be exercised in understanding the meaning of “not” in the phrase “not two” however. Zen insists that the “not” primarily refers to an existential, practical negation of the “I,” which the practitioner achieves by “up-rooting the ego-consciousness,” and in turn yields, by implication, a logical negation as well. This is because Zen thinks the practitioner cannot achieve this negation simply by following either-or logic, or for that matter by following the intellectual process of reasoning, because both logic and reasoning intrinsically involve two things, for example, the thinker and the thought. With either-or logic a mere logical negation involves an infinite regress in negating the “I”; one who negates the “I” retains the affirmative act of holding “I” in the mind as that which negates. And when the “I” further attempts to negate this affirming act, there still remains an “I” who negates it and the process goes on ad infinitum. For this reason, Zen recommends the practitioner to “forget the ‘I” when engaging oneself in any action, be it a mind-act, bodily-act, or speech-act, as is seen for example in both Dōgen and Takuan (1573–1645). 