Do Baha'is believe in miracles and supernatural beings (like angels, demons, and Jinn)?
What a great question!
While Baha'is acknowledge that miracles can occur we do not use them as "proofs" of the Manifestation in this dispensation.
I'll supply a few quotes from the Baha'i Writings:
Baha'u'llah Himself has indicated miracles and prodigies are not to be used...
We entreat Our loved ones not to besmirch the hem of Our raiment with the dust of falsehood, neither to allow references to what they have regarded as miracles and prodigies to debase Our rank and station, or to mar the purity and sanctity of Our name.
~ Baha'u'llah,
Epistle to the Son of the Wolf, p. 32
If we carefully examine the text of the Torah, we see that the Divine Manifestation never said to those who denied 35 Him, "Whatever miracle you desire, I am ready to perform, and I will submit to whatever test you propose." But in the Epistle to the Shah, Bahá'u'lláh said clearly, "Gather the 'ulama, and summon Me, that the evidences and proofs may be established."[1]
[1 Cf. p. 30, n.1. In giving such importance to this example of the good sense of Bahá'u'lláh,
'Abdu'l-Bahá means to emphasize the uselessness of miracles as a proof of the truth of the Manifestations of God. Cf. "Miracles," p. 100.]
(Abdu'l-Baha,
Some Answered Questions, p. 34)
For example, if we relate to a seeker, a stranger to Moses and Christ, marvelous signs, he will deny them and will say: "Wonderful signs are also continually related of false gods by the testimony of many people, and they are affirmed in the Books. The Brahmans have written a book about wonderful prodigies from Brahma." He will also say: "How can we know that the Jews and the Christians speak the truth, and that the Brahmans tell a lie? For both are generally admitted traditions, which are collected in books, and may be supposed to be true or false." The same may be said of other religions: if one is true, all are true; if one is accepted, all must be accepted. Therefore,
miracles are not a proof. For if they are proofs for those who are present, they fail as proofs to those who are absent.
~ Abdu'l-Baha,
Some Answered Questions, p. 100
Regarding supernatural beings:
"Ye are the
angels, if your feet be firm, your spirits rejoiced, your secret thoughts pure, your eyes consoled, your ears opened, your breasts dilated with joy, and your souls gladdened, and if you arise to assist the Covenant, to resist dissension and to be attracted to the Effulgence! Verily, I say unto you that the Word of God has assuredly been explained and has become an evident sign and a strong and solid proof, and its traces shall be spread in the East and West, and to these all heads shall bow and all souls shall submit and kneel down with their faces to the ground."
~ Abdu'l-Baha, Baha'i World Faith, p. 359
Regarding demons
"As to the question of evil spirits, demons and monsters, any references made to them in the Holy Books have symbolic meaning. What is currently known among the public is but sheer superstition."
(From a Tablet of 'Abdu'l-Bahá: Spiritualism and psychic Phenomena, p. 3)
(Compilations, Lights of Guidance, p. 512)