2. OBSERVATION.
Facts are acquired by means of observation. When the mind fixes the attention upon any phenomenon it observes it. The term observation means “to watch for” and may be defined as the act of watching for phenomena as they may occur. The observation may be only casual, or it may be willed or rational. It is the latter aspect which most concerns the logician. In this sense observation means careful, painstaking, systematic perception. It involves the concentration of consciousness upon the case in hand, or the actual giving of attention. The thing observed may be external, when the observation takes the form of sense-perception; or it may be internal, when the observation becomes a matter of introspection.