Answer:
To show the audience that he knows about many uses for herbs.
Step-by-step explanation:
The term soliloquy has the meaning of "speaking out loud". This is a concept associated with the monologue. Soliloquy is a type of speech that assumes that the character acts as if he were entirely unaccompanied, articulating and enunciating his thoughts and feelings aloud.
In "Romeo and Juliet", the soliloquy of Frei Laurence to show the public that he knows about many uses for herbs. That's because he keeps talking to himself about how flowers and plants can be the medicine and the poison for people. He also talks about how these herbs should be used wisely, because in the wrong person's hand the herbs can cause a lot of suffering.