the precursor of the Montessori method. Book III The third book concerns the selection of a trade. Rousseau believed it necessary that the child must be taught a manual skill appropriate to his gender and age, and suitable to his inclinations, by worthy role models. Book IV Once Emile is physically strong and learns to carefully observe the world around him, he is ready for the last part of his education—sentiment: "We have made an active and thinking being. It remains for us, in order to complete the man, only to make a loving and feeling being—that is to say, to perfect reason by sentiment". Emile is a teenager at this point and it is only now that Rousseau believes he is capable of understanding complex human emotions, particularly sympathy. Rousseau argues that, while a child cannot put himself in the place of others, once he reaches adolescence and becomes able to do so, Emile can finally be brought into the world and socialized. In addition to introducing a newly passionate Emile to society during his adolescent years, the tutor also introduces him to religion. According to Rousseau, children cannot understand abstract concepts such as the soul before the age of about fifteen or sixteen, so to introduce religion to them is dangerous. He writes: "It is a lesser evil to be unaware of the divinity than to offend it". Moreover, because children are incapable of understanding the difficult concepts that are part of religion, he points out that children will only recite what is told to them—they are unable to believe. Book IV also contains the famous "Profession of Faith of the Savoyard Vicar", the section that was largely responsible for the condemnation of Emile and the one most frequently excerpted and published independently of its parent tome. Rousseau writes at the end of the "Profession": "I have transcribed this writing not as a rule for the sentiments that one ought to follow in religious matters, but as an example of the way one can reason with one’s pupil in order not to diverge from the method I have tried to establish". Rousseau, through the priest, leads his readers through an argument which concludes only to belief in "natural religion": "If he must have another religion", Rousseau writes (that is, beyond a basic "natural religion"), "I no longer have the right to be his guide in that". Book V