The Trinity is a pagan concept. There is only one God — Jehovah — and Jesus
is a separate, created being. The holy spirit is God's active force, not a
person.
Read together. In verse 12, the speaker calls himself "the First and the Last" — a title Jehovah claims exclusively (Isa 44:6). In verse 13, the speaker says "my own hand laid the foundation of the earth" — clearly Yahweh. Then in verse 16, the same speaker says "the Sovereign Lord Jehovah has sent me, and his spirit." Yahweh is speaking — and says Yahweh sent him. This reveals plurality within the one God: the sent one is Yahweh, the sender is Yahweh, and the Spirit is a distinct party. This is exactly what Christians mean by the Trinity — not three gods, but one God who exists as Father, Son, and Spirit.
has Yahweh saying that Yahweh sent him — along with his Spirit. Three persons, one passage, all identified with the one God.
This is a prophetic voice change — Isaiah is now speaking, not Jehovah
Read the passage in context. Verse 12 starts with "Listen to me, O Jacob" and the speaker identifies himself as the First and the Last who laid the foundation of the earth. There is no voice-change marker. The speaker is clearly Yahweh all the way through to verse 16. Even the NWT's own cross-references connect this to Jehovah's speech.
The spirit is God's active force, not a person
Notice the grammar: "the Sovereign Lord Jehovah has sent me, AND his spirit." The spirit is listed alongside the sender and the sent one as a distinct party. An impersonal force doesn't get listed that way. Paul does the same in — "the grace of the Lord Jesus, the love of God, and the fellowship of the Holy Spirit." It's always a triad of persons, not two persons and a force.
This is just poetic language
The same passage contains concrete claims — laying earth's foundation, calling the stars. If those are literal, why treat the sending as merely poetic? The simplest reading is that Yahweh sent Yahweh — exactly what the Trinity explains.
Don't use the word "persons" without explaining it — JWs hear "three separate beings." Say "three who are each fully Yahweh" instead.
Read Isaiah 48 in the NWT, then focus on verses 12-16 until you can trace the speaker from memory: 'the First and the Last' in verse 12, the hand that laid the earth's foundation in verse 13, and 'the Sovereign Lord Jehovah has sent me, and his spirit' in verse 16. Compare so you can show that 'First and Last' belongs to Jehovah. Check the NWT cross-references at verse 16 yourself. Practise the doorstep question aloud, saying 'three who are each fully Yahweh' rather than 'persons'. Expect the reply that the voice changes to Isaiah, and rehearse showing that nothing marks a change of speaker between verses 12 and 16.