Three main pathways to explain this trend have been offered: placebo effect, focus and attitude adjustment, and activation of healing processes. These offerings have been expanded by Breslan and Lewis (2008) who have constructed a five pathway model between prayer and health with the following mediators: physiological, psychological, placebo, social support, and spiritual. The spiritual mediator is a departure from the rest in that its potential for empirical investigation is not currently feasible. Although the conceptualizations of chi, the universal mind, divine intervention, and the like breach the boundaries of scientific observation, they are included in this model as possible links between prayer and health so as to not unnecessarily exclude the supernatural from the broader conversation of psychology and religion. (However, whether the activation of healing processes explanation is supernatural or biological, or even both, is beyond the scope of this study and this article.)