And. . . It is not a locution, it is understood by 'narrowness' ('reduction, limitation'), and 'looks' in its meanings of 'looks, vision, intentions, aspirations', which can also be extended to 'knowledge, understanding'.
A phrase that means a person who has a lack of intellectual or moral breadth, and therefore his criteria, opinions and thoughts have a very poor baggage, and that in extreme cases give rise to fanaticism.