One could say that the power of any "domain of observation/action" can be substituted for "reason" in the above quote if the result is decreasing conditioning and increasing freedom of thought/action. This is to say that at any particular point in human development/evolution spirituality exists as a manner of freeing ourselves from unhealthy individual/collective habits. Spirituality is thereby merely that which at this moment enables an individual to grow (ethically, aesthetically, intellectually, physically, biologically). Spirituality dissipates the moment we stop growing. Thus, spirituality can be a continuum throughout life (one might even say that phylogeny is spiritual :-) )
Reason (as a human domain of action) has it's inherent limits. When individuals and societies recoil from these limits then reason becomes just another form of conditioned imprisonment.
Reason helped me to free myself from the conditioning of a Christian upbringing. Existential thought helped free me from the conditioning of a positivists/scientific training at the University. Reading the "denial of Death" back in '87 literally put the final nail in the coffin of my twin dogmas of Christian faith and scientific reason. Yogic practice and a melange of integral/systems thinkers are helping me to grow beyond the limits of existentialism...
Of course, Christianity, Science, Reason, Existentialism, Socialism, Capitalism,... remain as relative domains of existence that can dynamically compose and integrate a healthy living whole.
James
"Refracted rearwards along the course of evolution, consciousness displays itself qualitatively as a spectrum of shifting shades whose lower terms are lost in the night." - Teilhard de Chardin