Lesson 37 · Review
Four of these verbs — cessō, incipiō, possum, vetō — are marked "used with the infinitive." That is the lesson in miniature: they are incomplete until an infinitive finishes them.
A compound of potis, "able," and sum, "I am." Nothing about it needs memorising except one spelling rule — and that rule is decided entirely by the first letter of the form of sum it is glued to.
| Present indicative | Singular | Built from | Plural | Built from |
|---|---|---|---|---|
| 1st person | possum | potis + sum | possumus | potis + sumus |
| 2nd person | potes | potis + es | potestis | potis + estis |
| 3rd person | potest | potis + est | possunt | potis + sunt |
Where the form of sum begins with s, the prefix is written pos- and the two s's merge: pos+sum → possum, possumus, possunt. Where it begins with a vowel, the prefix keeps its t: pot+es → potes, potest, potestis. That is the whole irregularity.
sumus → possumus · estis → potestis · sunt → possunt
The other tenses give no trouble. The imperfect and future simply put pot- before the forms of sum; the perfect system is regular on the stem potu-.
| Tense | 1st sg. | 1st pl. | Formed on | English |
|---|---|---|---|---|
| Present | possum | possumus | pot-/pos- + sum | I am able, I can |
| Imperfect | poteram | poterāmus | pot- + eram | I was able, I could |
| Future | poterō | poterimus | pot- + erō | I shall be able |
| Perfect | potuī | potuimus | stem potu- | I have been able |
| Pluperfect | potueram | potuerāmus | stem potu- | I had been able |
| Future perfect | potuerō | potuerimus | stem potu- | I shall have been able |
The present infinitive is posse, "to be able"; the perfect is potuisse, "to have been able." Possum has no perfect passive participle — its principal parts stop at potuī — so it has no passive at all.
possum, posse, potuī, ——
The infinitive is a verbal noun: noun enough to be an object, verb enough to govern a case of its own. English does the same thing — "he ordered the men to flee" — and calls it an infinitive clause.
| Latin | English | Subject of infin. |
|---|---|---|
| Is virōs fugere iussit. | he ordered the men to flee | virōs (acc.) |
| Virī Gallōs castra pōnere vetuērunt. | the men forbade the Gauls to pitch camp | Gallōs (acc.) |
Verbs of wishing, commanding, forbidding and the like take an object clause made of an infinitive plus a substantive in the accusative — and that substantive is the subject of the infinitive, not the object of the main verb. Latin has no other case for it: an infinitive's subject is always accusative.
Is virōs fugere iussit. — he commanded the men to flee (it is the men who flee).
Some verbs cannot finish their own sentence. Possum, mātūrō, temptō, incipiō, cessō — say one aloud and you hear the gap where the infinitive belongs.
| Latin | English | Verb completed |
|---|---|---|
| Rōmānī Gallōs superāre possunt. | the Romans can conquer the Gauls | possunt |
| Bellum gerere mātūrant. | they hasten to wage war | mātūrant |
| Gallī esse līberī cessāvērunt. | the Gauls ceased to be free | cessāvērunt |
Here the infinitive has no subject of its own; it simply finishes the main verb, and the subject of the main verb does both actions. Compare Rule 3: if you can point to an accusative that performs the infinitive's action, it is a subject accusative; if the main subject performs it, the infinitive is complementary.
Diū sine aquā vīvere nōn potestis. — you cannot live long without water.
An adjective completing a complementary infinitive agrees in gender, number, and case with the subject of the main verb — not with the infinitive.
Malī puerī esse bonī nōn possunt. — bad boys cannot be good (bonī agrees with puerī).
English says "to see is to believe" and means "seeing is believing." Latin does exactly the same, most often with est — and treats the result as a neuter singular noun.
| Latin | English | Office |
|---|---|---|
| Superāre est grātum. | to conquer is pleasing | subject |
| Vidēre est crēdere. | to see is to believe | subj. & pred. nom. |
| Galbam superāre inimīcōs est grātum multīs. | for Galba to conquer his enemies pleases many | subj. + subj. acc. |
Because the noun-infinitive counts as neuter singular, any predicate adjective agreeing with it is neuter singular too: grātum, not grāta or grātus. And when such an infinitive takes a subject of its own, that subject is accusative, exactly as in Rule 3 — Galbam superāre…, "for Galba to conquer…"
Egēre cibō et vīnō est virīs molestum. — to lack food and wine is troublesome to men.
Six out of six before you start the exercises.
Question 1
Why is it possumus but potestis?
Right. The prefix is written pos- before a form of sum beginning with s, and pot- before one beginning with a vowel. Hence pos+sumus → possumus, but pot+estis → potestis. The perfect stem potu- belongs to potuī, and -tis is not passive.
Not quite — look at the form of sum hiding inside each word (sumus, estis). What is different about the letter each one starts with?
Question 2
What is the present infinitive of possum?
Right. Posse is the present infinitive ("to be able"); potuisse is the perfect infinitive ("to have been able"), built on potu-. Possere does not exist — possum is a compound of sum, not a third-conjugation verb.
Not quite — possum is potis + sum, so its infinitive is built on esse. What does pot- + esse contract to?
Question 3
In Is virōs fugere iussit, what is virōs?
Right. Virōs is accusative, and it is the subject of fugere — the men are the ones who flee. The subject of an infinitive is always accusative. The subject of iussit is is, "he."
Not quite — who does the fleeing in this sentence? Whoever that is stands as the infinitive's subject, and Latin puts it in one particular case.
Question 4
In Rōmānī Gallōs superāre possunt, what kind of infinitive is superāre?
Right. Possum is a verb of incomplete predication, so superāre completes it: "the Romans are able to conquer." Gallōs is the object of superāre, not its subject — the Romans do the conquering. Compare Is virōs fugere iussit, where the accusative really is the subject.
Not quite — ask who does the conquering. If it is the main subject (Rōmānī), the infinitive is not carrying a subject of its own; it is finishing the main verb.
Question 5
In Malī puerī esse bonī nōn possunt, why is bonī masculine nominative plural?
Right. The adjective looks past the infinitive to the subject of the main verb: puerī is masculine nominative plural, so bonī is too. It is not genitive here, and it does not agree with esse — that would only happen if the infinitive were itself the subject (Rule 6).
Not quite — who is being called good? Find the subject of possunt, and make the adjective match it in gender, number, and case.
Question 6
In Superāre est grātum, why is grātum neuter singular?
Right. Superāre here is a pure noun — the subject of est — and a noun-infinitive is neuter singular. The predicate adjective must therefore be neuter singular: grātum. Nothing is understood, and the infinitive is not accusative.
Not quite — what is the subject of est in this sentence? Whatever gender and number that subject counts as, the predicate adjective must match.
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