I just finished co-running Stoic Camp New York-2017, together with my friend Greg Lopez. We had 20 students and an amazing time up in Stony Point, on the West Bank of the Hudson River, north of New York. As part of the introductory session, we went through the basics of Stoic theory as reported by Diogenes Laertius in book VII of his Lives and Opinions of the Eminent Philosophers, which covers the early and middle Stoa (i.e., before Seneca, Musonius, Epictetus and Marcus). I’m going to propose the passages we used here, organized by subject matter, as a handy vademecum for the Stoic practitioner. Each section below begins with a selection of pertinent quotes from Diogenes, and ends with a mini summary and commentary of my own. I hope it’s going to be useful.
The parts of philosophy
 Philosophic doctrine, say the Stoics, falls into three parts: one physical, another ethical, and the third logical.
 They liken Philosophy to a fertile field: Logic being the encircling fence, Ethics the crop, Physics the soil or the trees. … No single part, some Stoics declare, is independent of any other part, but all blend together.
 Diogenes of Ptolemaïs, it is true, begins with Ethics; but Apollodorus puts Ethics second, while Panaetius and Posidonius begin with Physics, as stated by Phanias, the pupil of Posidonius, in the first book of his Lectures of Posidonius.
This is the classic division of philosophy into three fields: logic (having to do with good reasoning), physics (understanding of the world), and ethics (how to live one’s life). The three are connected in that — as in the analogy of the garden — the logic and physics are necessary to protect (from bad reasoning) and nurture (through a sound understanding of the cosmos) the ethics. Notice that there was disagreement among the Stoics on the best way to set up the curriculum, one of a number of pieces of evidence that the philosophy was open to internal disagreement, not run like a cult (in the way of the Pythagoreans, for instance).
The nature of impressions
 A presentation (or mental impression) is an imprint on the soul: the name having been appropriately borrowed from the imprint made by the seal upon the wax.
 Freedom from precipitancy is a knowledge when to give or withhold the mind’s assent to impressions. By wariness they mean a strong presumption against what at the moment seems probable, so as not to be taken in by it.
 Without the study of dialectic, they say, the wise man cannot guard himself in argument so as never to fall; for it enables him to distinguish between truth and falsehood, and to discriminate what is merely plausible and what is ambiguously expressed, and without it he cannot methodically put questions and give answers.
 Overhastiness in assertion affects the actual course of events, so that, unless we have our perceptions well trained, we are liable to fall into unseemly conduct and heedlessness.
 For presentation comes first; then thought, which is capable of expressing itself, puts into the form of a proposition that which the subject receives from a presentation.
 Again, some of our impressions are scientific, others unscientific: at all events a statue is viewed in a totally different way by the trained eye of a sculptor and by an ordinary man.
“Impressions” are a combination of sensorial input and automatic judgment, as, for instance, when I suddenly feel fear because I have heard an unfamiliar sound in the house at night. Impressions ought to be examined in the light of reason, so that we can decide whether to give assent to them or not. This requires a certain degree of cognitive distancing (avoiding overhastiness), and also the ability to engage in sound reasoning (logic). This is the basis of Epictetus’ discipline of assent, which Pierre Hadot connects with the topos of logic and the virtue of prudence (practical wisdom). Notice that practice makes for better (more “scientific”) judgments of impressions.
Living according to nature
 An animal’s first impulse, say the Stoics, is to self preservation, because nature from the outset endears it to itself, as Chrysippus affirms in the first book of his work On Ends.
 And nature, they say, made no difference originally between plants and animals, for she regulates the life of plants too, in their case without impulse and sensation, just as also certain processes go on of a vegetative kind in us. But when in the case of animals impulse has been superadded, whereby they are enabled to go in quest of their proper aliment, for them, say the Stoics, Nature’s rule is to follow the direction of impulse. But when reason by way of a more perfect leadership has been bestowed on the beings we call rational, for them life according to reason rightly becomes the natural life. For reason supervenes to shape impulse scientifically.
 This is why Zeno was the first (in his treatise On the Nature of Man) to designate as the end “life in agreement with nature” (or living agreeably to nature), which is the same as a virtuous life. … Again, living virtuously is equivalent to living in accordance with experience of the actual course of nature, as Chrysippus says in the first book of his De finibus; for our individual natures are parts of the nature of the whole universe.
 And this is why the end may be defined as life in accordance with nature, or, in other words, in accordance with our own human nature as well as that of the universe. … And this very thing constitutes the virtue of the happy man and the smooth current of life.
 By the nature with which our life ought to be in accord, Chrysippus understands both universal nature and more particularly the nature of man, whereas Cleanthes takes the nature of the universe alone as that which should be followed, without adding the nature of the individual.
So the Stoics had what we would today call an evolutionary theory of virtue (just like their “cradle argument” was a theory of human developmental psychology, connected to the concept of oikeiosis): plant life is regulated without impulses and sensation, which however do play a role in animal and human life. But human beings have reason as well. So to apply reason to the question of how to live is the same as living according to nature. If you do that, according to the Stoics, you figure out that this specifically means living a life of virtue (though Diogenes doesn’t say this here, that’s because virtue is the only thing that is always useful to improve the human lot, an argument that goes back to Socrates in the Euthydemus). Notice two more things: first, the reference to a smooth flow of life if we live virtuously; second, again, vibrant disagreement among the Stoics on specific issues of doctrine, in this context whether we should think in terms of human nature or the nature of the cosmos at large.
 Virtue, in the first place, is in one sense the perfection of anything in general, say of a statue; again, it may be non-intellectual, like health, or intellectual, like prudence.
 That it, virtue, can be taught is laid down by Chrysippus in the first book of his work On the End, by Cleanthes, by Posidonius in his Protreptica, and by Hecato; that it can be taught is clear from the case of bad men becoming good.
 Panaetius, however, divides virtue into two kinds, theoretical and practical; others make a threefold division of it into logical, physical, and ethical; while by the school of Posidonius four types are recognized, and more than four by Cleanthes, Chrysippus, Antipater, and their followers. Apollophanes for his part counts but one, namely, practical wisdom. Amongst the virtues some are primary, some are subordinate to these. The following are the primary: wisdom, courage, justice, temperance. Particular virtues are magnanimity, continence, endurance, presence of mind, good counsel. And wisdom they define as the knowledge of things good and evil and of what is neither good nor evil; courage as knowledge of what we ought to choose, what we ought to beware of, and what is indifferent.
 Similarly, of vices some are primary, others subordinate: e.g. folly, cowardice, injustice, profligacy are accounted primary; but incontinence, stupidity, ill-advisedness subordinate. Further, they hold that the vices are forms of ignorance of those things whereof the corresponding virtues are the knowledge.
 Virtue itself and whatever partakes of virtue is called good in these three senses — viz. as being (1) the source from which benefit results; or (2) that in respect of which benefit results, e.g.the virtuous act; or (3) that by the agency of which benefit results, e.g. the good man who partakes in virtue.
To begin with, the word “virtue” (arete, in Greek) applies to any kind of human excellence, of which the moral (intellectual) virtues are a subset. Diogenes lists the four cardinal Stoic virtues, but makes clear that there are several sub-virtuous, so to speak. The full list is detailed in a table on p. 28 of this paper by Matthew Sharpe on Stoic virtue ethics. Well worth the reading. Diogenes then says that to each virtue corresponds a given vice, and — most importantly — that virtue is a type of knowledge, and vice a type of ignorance (best understood as unwisdom). Notice, once more, evidence of debate among the Stoics on all these subject matters.
Preferred vs dispreferred indifferents
 Goods comprise the virtues of prudence, justice, courage, temperance, and the rest; while the opposites of these are evils, namely, folly, injustice, and the rest. Neutral (neither good nor evil, that is) are all those things which neither benefit nor harm a man: such as life, health, pleasure, beauty, strength, wealth, fair fame and noble birth, and their opposites, death, disease, pain, ugliness, weakness, poverty, ignominy, low birth, and the like. This Hecato affirms in his De fine, book vii., and also Apollodorus in his Ethics. and Chrysippus. For, say they, such things (as life, health, and pleasure) are not in themselves goods, but are morally indifferent, though falling under the species or subdivision “things preferred.”
 Further, they say that that is not good of which both good and bad use can be made; but of wealth and health both good and bad use can be made; therefore wealth and health are not goods.
 The term “indifferent” … denotes the things which do not contribute either to happiness or to misery, as wealth, fame, health, strength, and the like; for it is possible to be happy without having these, although, if they are used in a certain way, such use of them tends to happiness or misery.
 Of things indifferent, as they express it, some are “preferred,” others “rejected.” Such as have value, they say, are “preferred,” while such as have negative, instead of positive, value are “rejected.” Value they define as, first, any contribution to harmonious living, such as attaches to every good; secondly, some faculty or use which indirectly contributes to the life according to nature: which is as much as to say “any assistance brought by wealth or health towards living a natural life”; thirdly, value is the full equivalent of an appraiser, as fixed by an expert acquainted with the facts — as when it is said that wheat exchanges for so much barley with a mule thrown in.
 Again, of things preferred some are preferred for their own sake, some for the sake of something else, and others again both for their own sake and for the sake of something else. … Things are preferred for their own sake because they accord with nature; not for their own sake, but for the sake of something else, because they secure not a few utilities.
An important bit here is the very clear explanation that preferred indifferents are so-called because they have “value” (that’s why they are preferred) but they do not affect our moral character (indifferent). I have explained this concept in earlier writings in terms of what modern economists call lexicographic preferences. Notice, at , a piece of syllogistic reasoning aiming to prove that wealth, health, etc. are not “goods.” Once you understand how the Stoics used these terms, it becomes obvious why this is true: wealth, for instance, can be used to do good as well as to do evil, therefore it is logically independent of good and evil, and so it is not, by itself, good or evil (though one can use it in good or evil fashion). At  we get a pretty clear explanation of why certain things are preferred (or dispreferred): either they contribute to harmonious living, or to the life according to nature, or because of the barley and the mule thing…
On good and bad emotions
 Passion, or emotion, is defined by Zeno as an irrational and unnatural movement in the soul, or again as impulse in excess. The main, or most universal, emotions, according to Hecato in his treatise On the Passions, book ii., and Zeno in his treatise with the same title, constitute four great classes, grief, fear, desire or craving, pleasure.
 They hold the emotions to be judgements, as is stated by Chrysippus in his treatise On the Passions: avarice being a supposition that money is a good, while the case is similar with drunkenness and profligacy and all the other emotions. Pity is grief felt at undeserved suffering; envy, grief at others’ prosperity; jealousy, grief at the possession by another of that which one desires for oneself; rivalry, pain at the possession by another of what one has oneself.
 Fear is an expectation of evil.
 Desire or craving is irrational appetency, and under it are ranged the following states: want, hatred, contentiousness, anger, love [meaning irrational, obsessive passion], wrath, resentment. … Hatred is a growing and lasting desire or craving that it should go ill with somebody.
 Wrath is anger which has long rankled and has become malicious, waiting for its opportunity. … Resentment is anger in an early stage. Pleasure is an irrational elation at the accruing of what seems to be choiceworthy. … Malevolent joy is pleasure at another’s ills.
 And as there are said to be certain infirmities in the body, as for instance gout and arthritic disorders, so too there is in the soul love of fame, love of pleasure, and the like. … And as in the body there are tendencies to certain maladies such as colds and diarrhoea, so it is with the soul, there are tendencies like enviousness, pitifulness, quarrelsomeness, and the like.
 Also they say that there are three emotional states which are good, namely, joy, caution, and wishing. Joy, the counterpart of pleasure, is rational elation; caution, the counterpart of fear, rational avoidance. … And they make wishing the counterpart of desire (or craving), inasmuch as it is rational appetency. … Thus under wishing they bring well-wishing or benevolence, friendliness, respect, affection; under caution, reverence and modesty; under joy, delight, mirth, cheerfulness.
 Now they say that the wise man is passionless, because he is not prone to fall into such infirmity [i.e., unhealthy passions].
This is a pretty complete treatment of the oft-misunderstood topic of Stoic emotions. It should be clear, however, that the Stoics sought to avoid only the unhealthy emotions, what they called “passions” (pathē), and to nurture healthy emotions (eupatheiai). Diogenes gives a lengthy list of both, so to thoroughly explain what the Stoics meant. Notice, incidentally, the common parallel in Stoicism between physical and mental / spiritual health. At  we are introduced to the Stoic theory that emotions are a form of judgment, i.e., they have a cognitive component. So the “impressions” from above, which are automatic, generate a sort of proto-emotions (propatheiai), and it is to those that we apply our judgment. If we do this incorrectly, we turn the proto-emotion into an unhealthy passion. Schematically:
propatheiai + incorrect assent => pathē
Something like this is confirmed by modern cognitive science, where neuroscientists talk of “fear,” say, referring to the involuntary feeling arising from the rush of adrenalin when we perceive a threat, while psychologists use the same word referring to the mature, cognitively mediated emotion of the type “I ought to be afraid of terrorist attacks.” So when the Stoics say that the wise person is “passionless” (apatheia) they don’t mean that she lacks all emotions, but that she is unaffected by unhealthy one, as in:
propatheiai + correct assent => apatheia
The goal of Stoicism here is to produce emotionally healthy individuals. Hard to object to it, no?
That’s Stoicism in a nutshell! Let me leave you with a bonus quotation from Diogenes:
 They will take wine, but not get drunk.