Le/la vs lui?
I never know when to use le/la or lui when doing the "je le vois" word arrangement. So, when to use le/la or lui?
It depends on whether the object of the verb is direct or indirect. A direct object has no preposition in front of it while an indirect object does have a preposition. An example can be given with the verb to give/ donner.
I give the chair to Luke=> Je donne la chaise à Luke
In this case chair is the direct object since there is no preposition in between it and the verb. Luke is the indirect object because there is the preposition to/à in the way of the verb.
To replace direct objects, you use le/la/l'. In this case 'la' will replace the chair. For indirect objects, you use lui/leur . In this case 'lui' will replace Luke
I give him it. Je lui la donne.
With the verb voir, it almost always takes a direct object. Even if you are seeing Luke, a person, you will use 'le' because there is no preposition in the way of him and the verb.
Je vois Luke => Je le vois.
Of course there are some difference between the languages for what takes a direct or indirect object. I listen to music => J'écoute le musique In English music is an indirect object while in French it is a direct object.
Hoped that helped.
It's in French, but you should understand it at level 13. Or for an English version: