"-In farther confirmation of this reasoning, it may be remarked, that if the perception of visible figure were an immediate consequence of the picture on the retina, we should have at the first glance as distinct an idea of a figure of a thousand sides, as of a tri: angle or a square. The truth is, that when the figure is very simple, the process of the mind is so rapid, that the perception seems to be instantaneous ; but when the sides are multiplied beyond a certain num ber, the interval of time necessary for these different acts of attention becomes perceptible. It may per haps be asked, what I mean by a point in the outline of a figure, and what it is that constitutes this point one object of attention ? The answer, I apprehend, is, that this point is the 'minimum visibile. If the point be less, we cannot perceive it : if it be greater, it is not at all seen in one directiOn." Elements of the Phi losophy of-the Human Mind, c. 2.
This doctrine, however, that the mind is incapable . of attending to more than a single object, at one and the same instant of time, has been controverted by various able philosophers, who conceive it to be found ed on a false analogy supposed to exist between the properties of body and those of mind. Material space, it is well known, must completely occupied by a single body, to the exclusion ofevery other from that portion of it which the body fills ; but what reason have we to ascribe such a quality as this to mind ?. Where is the analogy between the understanding and external space ; or between a mere notion of the in tellect, and an impenetrable piece of matter ? On the contrary, there seems a kind of necessity, in certain cases, for admitting that the mind can attend at the same moment to objects which may also be made se parate objects of attention, otherwise it does not ap pear how the relations and points of comparison be tween those objects can be satisfactorily understood. How, for example, can we discern the harmony be tween two musical notes, unless both are present to the mind together ? Or bow can we draw a conclu sion from a comparison of two or more connected truths, unless we contemplate these truths in the mind at one and the same moment ? Every syllogism is formed, by comparing together two propositions, cal.
led the major and the minor ; and it seems necessary, before we can form a legitimate inference, that these two propositions should, at the same instant, be ob jects of our attention. • " Many single words," says Dr Gregory, " for example prepositions, and most sentences, denote some kind of relation ; but we cannot, I think, conceive a relation, without thinking at once of the things (two or more) that are related, as well as of the relation (both in its generic and in its specific nature) that sub sists between them." This author is of opinion, that, with respect to the moods and other inflections ofverbs, there cannot be a doubt that they are employed to denote combinations of simultaneous thoughts, no one of which can reasonably be said to occur to the person speaking, or to be apprehended by the person hear ing, before the rest : and that all nouns, even proper names, denote a congeries of circumstances, or mass (not a train) of thoughts, which are conceived at once, and cannot be separated and considered in suc cession, but by a very laborious effort. See Theory of the Illoods of Verbs, Edin. Phil. Trans. vol. ii.
Various remarkable examples are upon record of the great power of undivided attention possessed by certain individuals, and of the capacity of apparently attending at the same moment to more than one im portant and interesting concern. Fontenelle relates of the celebrated mathematician Montmort, that he could command his attention at pleasure, insomuch, that in the same chamber where he was at work on the most complicated problems, his children might be as noisy as they pleased, or might dance and play upon the harpsichord. The famous chess-player Phi. lidor, it is well known, could direct three games of chess at the same instant, of one of which only be re. quired ocular inspection, the moves of the other two being merely announced to him by an assistant. And it is recorded of Julius Crsar, that while he was writing a dispatch, he could at the same moment die , tate four others to his secretaries : if he did not write himself, he could dictate seven letters at once. See Stewart's Phil. of the Mind, c. 2. Helvetius De l'Esprit. Condillac Stir l'Oriaine des Connoiss. Hum. s. 2. c. 1. Reid's Intel. and Active Porcers. (m)