Can a prepositional phrase act as the direct object?

Question

I'm new to Esperanto and starting to use transitive verbs. The book I'm using, A Complete Grammar of Esperanto (Ivy Kellerman, 1910), states that "a transitive verb expresses an act of the subject upon some person or thing". It also states that "the person or thing acted upon is called the direct object of a transitive verb, and is given the ending -n". This seems to imply that the direct object has to be a noun.

However, Plena Ilustrita Vortaro de Esperanto gives the example sentence "mi rigardis tra fenestro de mia domo" here. Since "rigardi" is a transitive verb, the prepositional phrase "tra fenestro de mia domo" must be acting as the direct object. So it seems valid to use a prepositional phrases as the direct object.

And just for comparison's sake, if the sentence was instead "mi rigardis", it would be invalid because "rigardi" is transitive. And if the sentence was instead "mi rigardis la ĉevalojn tra fenestro de mia domo", the direct object would now be "la ĉevalojn" instead of the prepositional phrase.

Could someone provide an official or a credible source which explicitly outlines this grammatical rule? I'm trying to learn Esperanto with a firm understanding of all the constructed grammatical rules.

Answer 1

A transitive verb just means that the verb is an action upon something else. However you don’t necessarily have to mention the object and it can just be implied. For example:

What are you doing?

I am reading.

In this case to read is a transitive verb. The person asking the question will assume the other person is reading something, probably a book, so the verb is still transitive even though the sentence doesn’t have an explicit object.

This is the same thing that is happening with your example sentence. The tra part is not the object. Instead the object is not explicitly mentioned and the reader is supposed to assume that the person is looking at something out of the window, even though they don’t explicitly mention it.

Kion vi faras?

Mi rigardas [ion] tra la fenestro.

Answer 2

Plena manlibro de Esperanta gramatiko (PMEG) is your friend. It's available online, as downloadable html site and as PDF. It explains the grammar of Esperanto thoroughly… in Esperanto, so it might have a steep learning curve.

PMEG, usually called by its nickname Pomego, is constantly updated. The latest revision is from 2019-10-16.

To answer your question see the tra examples in PMEG, especially the one with the verb rigardi.