Learn Hardcore Latin: Ego mendacio non credo, sed veritati credo. - I do not believe a lie, but I believe the truth.

Yes: credo already means I believe. Latin often drops the subject pronoun. Ego is added for emphasis or contrast, like I (as opposed to someone else) don’t believe a lie, but I do believe the truth.

Why does credo take mendacio and veritati instead of something like an accusative?

With credere meaning to believe / to trust, Latin commonly uses the dative for the person/thing believed or trusted. So:

mendacio = dative singular of mendacium (to a lie / in a lie)
veritati = dative singular of veritas (to the truth / in the truth)

So the structure is basically I give belief to X → I believe X.

How do I know mendacio is dative and not ablative?

Formally, mendaciō (2nd declension singular) can be dative or ablative. Context and verb choice decide it: credere normally governs the dative, so here it’s read as dative. (If it were ablative, you’d expect a different construction or meaning.)

Why is it veritati (dative), not veritatem (accusative)?

Because credere in this sense typically takes the dative. If you used veritatem (accusative), you’d be pushing toward a different phrasing (often with other verbs or with a different nuance). The idiomatic Latin for “believe the truth” is veritati credere.

What’s the difference between mendacium and mendacium as “a lie” vs “lying” in general?

Mendacium can mean a single lie (a specific false statement), but it can also function more generally as falsehood/lying depending on context. In this sentence, the singular works well as an abstract idea: I don’t believe in falsehood, but (I do believe) in truth.

Why is non placed before credo? Could it go elsewhere?

Non often comes right before the word it negates, and placing it before the verb (non credo) is very common. You could also write mendacio credo non in poetry or for special emphasis, but in normal prose mendacio non credo / non credo mendacio are the standard options, with slightly different emphasis.

What does sed do here, and how strong is it?

Sed means but and introduces a contrast. It’s a straightforward adversative conjunction: I don’t believe a lie, but I believe the truth. It’s stronger and more direct than something like autem (however), which is often softer and more “add-on.”

Why is credo repeated? Could Latin omit the second credo?

Repeating credo makes the parallelism very clear and emphatic: non credo … sed … credo. Latin can omit repeated verbs (ellipsis), and Ego mendacio non credo, sed veritati (credo) would be understandable, but the repetition is clean and rhetorically punchy.

Is the word order “normal”? Why does mendacio come before non credo?

Latin word order is flexible. A very common prose pattern is to place important elements earlier. Here, putting mendacio first highlights what is being rejected, then veritati highlights what is accepted. Both mendacio non credo and non credo mendacio are fine; the first can feel slightly more focused on the lie.

What tense is credo and does it mean “I believe” or “I am believing”?

Credo is present indicative active. In Latin, the present can cover both I believe and I am believing, but English usually prefers the simple present I believe for general statements like this.

Why is veritati dative -i but mendacio is -o?

They’re from different declensions:

mendacium, mendaciī is 2nd declension neuter → dative singular mendaciō
veritas, veritātis is 3rd declension feminine → dative singular veritātī

Same case (dative), different endings because of declension patterns.

How would pronunciation work for mendacio and veritati?

In a common classroom (restored) pronunciation:

mendaciō: men-DA-ki-oh (with ci = “ki”)
veritātī: weh-ree-TAH-tee (long ā and long final ī)

In ecclesiastical pronunciation:

mendaciō: men-DAH-cho (with ci before a vowel = “ch”)
veritātī: veh-ree-TAH-tee