It cannot be denied that what we call knowledge is concerned with the discrimination of valid meaning. To know is to appreciate the _meaning_ of things and the meaning _of things_ is the same with valid meaning. Judging determines knowledge, and in the same act develops meaning. To put it otherwise, knowledge is a matter of _content_; _content_ is _meaning_, and we have knowledge when we have meaning satisfactorily determined. It is evident, therefore, that if we would understand the judging-function, we must first make clear to ourselves the nature and rôle of _meaning_. Meaning is universally embodied in _ideas_. To know, to understand the meaning, to get ideas, are the same. Now, in ideas two factors may be distinguished. First, every idea has as its base an image or emphasized portion of experience. In some forms of ideation we are more immediately aware of the presence of images than in others, but no idea--even the most abstract--can exist apart from an ultimate base. Second, every idea is equally a function of _reference_ and _control_. As _reference_, the idea projects in the mind's view an anticipation of experiences and of the conditions upon which these experiences depend for their realization; as _control_, ideas are agencies in turning anticipations into realizations.[54] To be more specific on both points: Since the days of Galton it has been almost a commonplace in psychology that ideas are embodied in forms of imagery which vary for and in different individuals. It has been maintained, it is true, that in abstract forms of thought, imagery disappears. This objection is met in two ways. For one, words--the vehicle of many abstract ideas--involve imagery of a most pronounced type: for another, every idea, when examined closely, discloses an image, no matter how much for the time being this has been driven into obscurity by the characteristics of reference and control. Furthermore, when we examine the anticipatory aspect of ideas, the presence of imagery both with reference to outcome and to conditions is so evident that its presence will scarcely be denied.