You are already familiar with the modal verb moeten for expressing obligations ("to have to"). However, just like in English, Dutch speakers also use moeten to express logical certainty or a strong deduction. When the evidence points to a single conclusion, something must be true.
Logical certainty
When using moeten for a deduction, it acts as a standard modal verb. It takes the second position in the sentence, and the main verb (often zijn) is pushed to the very end.
| According to this theory, that must be the conclusion. | Volgens deze theorie moet dat de conclusie zijn. |
| I see a pattern, so there must be a connection. | Ik zie een patroon, dus er moet een verband zijn. |
Drawing conclusions
When talking about science, puzzles, or mysteries, you will often state a known fact and follow it up with a logical deduction. The conjunction dus (so) is perfect for linking your evidence to what must be the case.
| The formula is easy, so the solution must be here. | De formule is makkelijk, dus de oplossing moet hier zijn. |
| The proof is missing, so the perpetrator must be very smart. | Het bewijs ontbreekt, dus de dader moet heel slim zijn. |
Talking about deductions
To talk about the act of making a logical inference, you can use the separable verb afleiden (to deduce).
| to deduce | afleiden |
When you combine moeten with multiple verbs (like kunnen and afleiden), moeten stays in the second position, and all the infinitives cluster together at the end of the clause.
| From the experiment you must be able to deduce the truth. | Uit het experiment moet je de waarheid kunnen afleiden. |