**11.  If fears relating to the heavens did not disturb us, and if the terrors of death did not concern us, and if we had the courage to contemplate the natural limits of pain and of desire, we would have no need to study the nature of things.**

Alternate Translations: Bailey:  If we were not troubled by our suspicions of the phenomena of the sky and about death, fearing that it concerns us, and also by our failure to grasps the limits of pains and desires, we should have no need of natural science.   Yonge:  If we were not troubled by our suspicions of the phenomena of the sky and about death, fearing that it concerns us, and also by our failure to grasps the limits of pains and desires, we should have no need of natural science.

Letter to Pythocles: Know then, that the only aim of the knowledge of the heavenly phenomena, both those which we can observe directly, and those on which we can only speculate, is freedom from anxiety, and the calmness which is derived from a firm belief; and this is the aim of every science.

Letter to Herodotus: As for the theoretical knowledge of the rising and setting of the stars, of the movement of the sun between the tropics, and of the eclipses, and all other similar phenomena, that is utterly useless as far as having any influence upon happiness. Moreover, those who possess knowledge of the movement of the stars, but are nonetheless ignorant of Nature and of the most probable causes of that movement, are no more protected from fear than if they were in the most complete ignorance. Such men experience the most lively fears, for the knowledge of the motion of the stars that they do possess inspires in them troubles which they cannot resolve, and those troubles cannot be dissipated except through a clear perception of the reasons for these phenomena.  As for us, we find many explanations of the motions of the sun, of the rising and setting of the stars, of the eclipses, and of similar phenomena. One must not think that this method of explanation is insufficient to procure happiness and tranquility. Let us content ourselves with examining how it is that similar phenomena are brought about directly under our own eyes, and let us apply these observations to the heavenly objects and to everything which is known only indirectly. Let us despise those people who are unable to distinguish those facts which may be explained in various ways from those facts which can only be explained in one single way. Let us disdain those men who do not understand the means of explaining the heavenly phenomena in ways that do not excite fear in us.

Once we understand that a phenomenon can be brought about by Nature in any of several natural ways, rather than by the gods in a way that inspires fear, we shall not be more troubled at the sight of it than if we actually knew the real cause.  We must also recall that the thing which principally troubles the spirit of men is the persuasion which they cherish that the stars are gods, [which we must always remember are] beings that are imperishable and perfectly happy. Such men fear that their thoughts and actions are displeasing to the will of these superior beings. Deluded by these fables, such men fear an eternity of punishment, and they fear the insensibility of death, as if that could affect them. What do I say? It is not the falseness of their beliefs, but their lack of knowledge and blindness, which governs them in all things. This is true to such a degree that, not even considering the truth of whether they really fear their gods, they are just as much troubled as if they really believed in these vain phantoms.  Real freedom from this kind of trouble consists in being emancipated from all these things, and in preserving the recollection of the principles which we have established, especially those that are most essential. Accordingly, it is well to pay careful attention to the phenomena with which we are familiar and to the sensations, both general and particular, which we have confirmed to be true. In sum, we must take note of the immediate evidence which each of our faculties furnishes to us. For if we pay attention to those points where uncertainty arises, we shall divine the causes of confusion and fear correctly. In this way we may trace back the heavenly phenomena to their causes, and deliver ourselves from those feelings which inspire the common people with extreme terror at every step.

NewEpicurean Commentary: Many circumstances, including religion and some philosophers, call out to us to adopt false opinions.  We are not born with knowledge of the phenomena we see in the skies; the seas seem mysterious, the diseases we suffer from seem inexplicable, death seems to be a horrible fate, and great danger is posed to us by those religions and philosophies who seek to deceive us into following them rather than the guidelines set by Nature.  If these dangers did not exist and did not cause us to be fearful and deprive us of joy of mind, we would have no reason to study science or philosophy.  It is for this reason, and this reason alone, that we study science and philosophy, as those are the antidote to all false opinion and terrors of the mind.  Note that we say “this reason alone” not to disparage the study of the study of Nature, but to reinforce that everything we do is for the attainment of a happy life.  Far from disparaging the study of Nature, in recognizing that this study is required for a happy life we recognize how important the study of Nature is.