Making deductions from clues in Brazilian Portuguese

Level B2

Making deductions from clues in Brazilian Portuguese

Brazilian Portuguese uses dever for a strong deduction, poder for a possible explanation, and não poder to rule something out. These verbs can describe your judgment of the evidence rather than an obligation, permission or ability. As in English, distinguish what the clues suggest from what you actually witnessed.

Dever and não poder: drawing conclusions

What you know and what you infer

The car outside and the bag on the desk are observed facts; Anna's location is a conclusion drawn from them. In “Ela deve estar em algum lugar do prédio.”, deve tells the listener that you are making a strong deduction.

By contrast, “Eu a vi na cozinha agora há pouco.” reports something you personally saw. English makes the same distinction between “she must be” and “I saw her”: do not add deve when you mean to report a directly known fact.

Strong deductions about the present: deve + infinitive

Use the present tense of dever followed by an infinitive when the clues strongly support a conclusion: “Ela deve estar em algum lugar do prédio.” Unlike English must, dever changes with its subject: ela deve, but eles devem.

For an action in progress, use estar followed by the -ndo form, as in “Eles devem estar trabalhando até tarde; as luzes do escritório deles ainda estão acesas.” Dever can also express obligation, so the surrounding clues establish the deduction meaning here.

Strong deductions about the past: deve ter + past participle

For a strong deduction about a completed event, use deve ter followed by a past participle: “O chão está encharcado; deve ter chovido durante a noite.” This corresponds to English “must have rained.”

Keep dever in the present when you are drawing the conclusion now; ter chovido places the inferred event in the past. With weather expressions such as chover, there is no subject pronoun corresponding to English it.

Possible explanations: pode and pode ter

Use poder when an explanation is possible but the clues do not justify a strong conclusion: “A tela está preta; a bateria pode estar descarregada.” Here pode means “might” or “could,” rather than permission or ability.

For a possible past event, use pode ter followed by a past participle: “Ela pode ter descido pra tomar um café.” English speakers may expect a separate word matching might, but present-tense pode naturally expresses this uncertainty. Pra is a common conversational form of para; use para in more formal writing.

Ruling out a present explanation: não pode + infinitive

Use não pode followed by an infinitive when the clues make a proposed explanation seem impossible: “Isso não pode ser o endereço certo; este prédio só tem dois andares.” This matches the deduction meaning of English “can't be.”

Não pode can also express a prohibition, but the address and the building's size show that this sentence rejects an explanation. Keep the negative with poder to express “can't”; não deve can instead mean “probably isn't” or express advice against something.

Ruling out a past event: não pode ter + past participle

Use não pode ter followed by a past participle to reject a possible past event: “Ela não pode ter ido pra casa; as chaves do carro ainda estão aqui.” This corresponds to English “can't have gone.”

Poder stays in the present because you are judging the evidence now; ter ido or ter pegado identifies the past event. In “Ele não pode ter pegado o trem; a linha ficou fechada o dia todo.”, the closed line is the reason for ruling out the train journey.

Finding Anna: clues, explanations and direct evidence

The dialogue combines observations with strong deductions, possible explanations and rejected possibilities. Tá is a common informal spoken form of está; use está in formal writing. Pra is likewise conversational, with para preferred in formal writing.

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