©The Royal Society/Richard Valencia.

Feijoo and his ‘Magisterio de la experiencia’ (lessons of experience), Part II

In my previous post I introduced a text by the Spanish priest Beníto Jerónimo Feijoo. We saw Feijoo giving his picture of the history of philosophy by telling a story of two ladies, Solidína (experience) and Ideária (Imagination), who attempt to conquer the kingdom named Cosmósia (the world). Feijoo sides with Solidína (experience) and in the rest of the essay he gives an argument for the adoption and promotion of the experimental method and the rejection of speculation unaided by experience.

The first thing he points out is

    … the little or no progress, which natural reason, unaided by experience, has made in the examination of the affairs of nature in the course of so many ages…What utility has the labours of so many men of excellent ingenuity, as have cultivated philosophy in the reasonable and speculative way, produced to the world? What art, either liberal or mechanical, of the many that are necessary for the service of man, or the good of the public, do we owe to speculative invention; and I might even say, what small advancement in any such art, has been derived from it?

Feijoo focuses on natural philosophy and medicine to show the errors of the way of philosophizing the schoolmen adhere to and teach by in the universities in Early Modern Spain. I will only consider here one of the examples he gives regarding natural philosophy. Feijoo comments on the discovery of the ‘pointing of the magnetic needle to the pole.’ His intention is to show that experience always needs to accompany all our reasonings. He tells us that the discovery of this property of the magnetic needle was first discovered in the thirteenth century, but the traditional way of philosophizing has prevented us from understanding how this property works:

    This admirable property [the pointing of the magnetic needle to the pole], which was totally unknown to the antients, was discovered in the thirteenth century, and immediately applied to the improvement of navigation. Upon its first discovery, the philosophers, according to their wonted custom of pretending to discern the causes of things, imputed this effect, as derived from an occult sympathy with the pole, contained in the very essence, form, and substance of the loadstone; and as this is supposed to be invariable, they concluded, that the direction must infallibly be invariable also.

However, experience proved them wrong and with time navigators noticed that the direction does vary and not always points directly to the pole. The philosophers had to reluctantly accept this even though they tried to discredit the observations of reliable navigators. But this didn’t deter them from making further speculations. Once it was discovered that at some places there is no variation of the direction of the needle, ‘under the meridian of the Azores,’

    … astronomers and geographers thought they had found out a fixed station, whereat to commence the first meridian… But this idea soon vanished, for a little while afterwards, they discovered two other meridians, where there was no variation… Upon this, they thought they had found out a certain principle, whereon to ground a compleat system for calculating or computing variations, by graduating them for the intermediate stations, in proportion to their greater or less distance from the mean space between the two places where there was no variation.

But once again a new discovery through experience disproved their speculations

    … they discovered, that this declination of the magnetic needle, varied more or less at the same place at different times, and that this change of variation was perpetual… In this instance, may be seen the fallibility of the most plausible reasonings unaccompanied by experiments.

Feijoo’s comments are very interesting. Notice that he is not saying that speculations themselves are the source of error, but rather he points out that they most certainly lead to error when unaided by experience. In the compass case the rules were at one instance deduced from experience, but once the speculative philosophers left experience aside they fell into error. Feijoo clarifies this thought in the following passage

    If the rules deduced from experimental observations are so fallible, that it is absolutely necessary in order to avoid all error, to pursue the thread of them so scrupulously, that reason should not venture to advance a step, without the light of an experiment appropriated to the business it is in search of; I say, if these rules are not to be relied on, what confidence can we place in those maxims, which derive their origin from our arbitrary ideas?

Feijoo is being very cautious here; he admits that even rules deduced from experience might be falsified, so we need to constantly check them with experiments and observations. Feijoo clearly prefers the method of experience, but he is also aware that experience sometimes can lead us astray. In the compass example shown above Feijoo tells us that our reasoning always needs to be aided by experimental observation. Further in the essay, as we will examine in a future post, he tells us that our senses alone are not enough for the acquisition of true knowledge, which can only be reached through reasoning and experience used together.

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