Most languages have two sets of words to express these two modes of understanding; one for the direct taking in or grasp of meaning, the other for its circuitous apprehension, thus: [Greek: gnônai] and [Greek: eidenai] in Greek; _noscere_ and _scire_ in Latin; _kennen_ and _wissen_ in German; _connaître_ and _savoir_ in French; while in English to be _acquainted with_ and to _know of or about_ have been suggested as equivalents.[22] Now our intellectual life consists of a peculiar interaction between these two types of understanding. All judgment, all reflective inference, presupposes some lack of understanding, a partial absence of meaning. We reflect in order that we may get hold of the full and adequate significance of what happens. Nevertheless, _something_ must be already understood, the mind must be in possession of some meaning which it has mastered, or else thinking is impossible. We think in order to grasp meaning, but none the less every extension of knowledge makes us aware of blind and opaque spots, where with less knowledge all had seemed obvious and natural. A scientist brought into a new district will find many things that he does not understand, where the native savage or rustic will be wholly oblivious to any meanings beyond those directly apparent. Some Indians brought to a large city remained stolid at the sight of mechanical wonders of bridge, trolley, and telephone, but were held spellbound by the sight of workmen climbing poles to repair wires. Increase of the store of meanings makes us conscious of new problems, while only through translation of the new perplexities into what is already familiar and plain do we understand or solve these problems. This is the constant spiral movement of knowledge. [22] James, _Principles of Psychology_, vol. I, p. 221. To _know_ and to _know that_ are perhaps more precise equivalents; compare "I know him" and "I know that he has gone home." The former expresses a fact simply; for the latter, evidence might be demanded and supplied. [Sidenote: Intellectual progress a rhythm]