Recognizing and Overcoming False Prophecies
We should first be reminded that living beings are either moral (God, angels and humans) or non-moral (animals, plants, fungi and single-celled organisms). Non-living things are of course, non-moral.
Generally, and in the broadest spiritual sense, prophecy is the information given completely by a moral being via spiritual means, to a human being (called a prophet) to be delivered intact and without any human input, to specified human recipients. Prophecy is thus seen as a three-element one-way spiritual communication process comprising of source, carrier and destination. Beyond this basic definition, the Scriptures further show certain details concerning the three elements and the information itself:
-- The source is always a moral being. To be designated a source of prophecy means to be the originator, author of the information, whether divine, angelic or human. However, only evil angelic beings (aka demons) will actually act as sources of prophecy. (Herein lies the root of the occult.) Righteous angels never do. Similarly, righteous humans would not ordinarily constitute themselves sources of prophecy. The only scriptural example where Aaron was a prophet of Moses was personally instituted by God Himself. (More on this later)
-- The carrier of the information can be any living being, whether moral or non-moral, but cannot be an inanimate thing. (Yes, even ordinary stones may be commissioned to raise praises to God if humans are negligent, but not to prophesy!). Generally, there is only one carrier per prophetic instance but sometimes, there is a hierarchy of carriers in which a primary carrier, typically angelic, receives the information directly from God, and delivers it to a secondary carrier, typically a human prophet, for onward delivery to the actual destination. This scenario is perfectly seen in certain parts of the prophecy of End Times as recorded in Daniel chapter 9. Also, the source may cause the same prophecy to be made multiple times, either concurrently or sequentially, and each such occasion is recognised as a distinct instance of the prophecy.
-- The destination is the recipient object on whom the information is to act or be acted upon. While the typical destination is humans, it can be any being whatsover, living or non-living.
-- The information in prophecy is not a mere message but an active word. It is a spiritual proclamation with an inherent ability in itself to be performed. This ability of course derives from the power of the source, whether divine or demonic. Typically the effect of the prophetic word is either to inform with a view to certain response on the part of the recipient or to cause a direct and practical alteration in the being and/or circumstances of the targeted object.
General Versus Biblical (True) Prophecy
At the general, conceptual level, any carrier (prophet) who is faithful to his/her spiritual source to accurately receive and execute the message is a "true" prophet in that regard. Thus, Jesus Christ, who as the Messiah, faithfully operates in the offices of King, Priest and Prophet, serves as an eminently true prophet of God. Similarly, Mohammed was a true prophet of Allah. And every faithful Yoruba babaláwo is a true prophet of Ọ̀rúnmìlà. The Bible also tells us about numerous prophets of Baal, Ashera, etc. And as previously mentioned, Aaron was a true prophet of Moses - at least while ministering in the courts of Pharaoh!
But then, what is the counsel of the Scriptures? Does faithfulness to source automatically define true prophecies and true prophets? The answer is a resounding No! There is the need to explore the very notion of truth and falsehood, and see how they apply to prophecies and prophets.
On Truth
The word of God is truth. Truth is constant and truth is one. It is therefore absolute rather than relative. Though the manifestation of truth to human beings is necessarily compartmentalised because of our nature (e.g. life, morality, integrity, divinity, eternal salvation, etc.), truth remains one in essence and these compartments or dimensions are mere differences of expression rather than fragments or divisions. Further, because of the limitations of human lives, it may be necessary to focus more on one dimension than another at one time or the other. This does not mean relativity of truth but grading of relevance to human experience. For example, a core dimension of truth is sacredness of human life which should propel us to do everything in our power to preserve it - both our lives and the lives of others whatever their circumstances and station in life (fetus, infant, aged, sick, atheist, Muslim, Christian, etc.). However, if there occurs a human situation which truly compels us to choose between sacredness of life and eternal salvation (another dimension of the same truth), we have to choose the later. (Daniel 3:16-18) In all this, truth remains one and absolute even when our experiencing of it is "graded".
Falsehood
Basically, falsehood is anything contrary to the truth, which is the word of God. We have noted that prophecies have the three elements of source, carrier and destination, together with the information transmitted. With this, it is immediately obvious that any content contrary to God's precepts is false. But this is not the whole of the matter. The word of God is not just letters of precepts but also its inherent Spirit which makes it a living entity. (Hebrews 4:12) The mere pronouncement of the "words" of God does not make it the word of God! The Source of the utterance must also be God. (Acts 16:16-18, Acts 19:14-16). Anybody can open the Bible and recite some favourite verses and anyone can hear a word from a genuine prophet of God and repeat it to some other people. If such proclamations are not authorised by God, the message is false even though it may coincide with the original divine words. And one more thing, such an occurrence is actually a theft (or should we saw spiritual plagiarism? Jeremiah 23:30). Who will deny that stealing is contrary to the word of God (the truth), and thus proved to be false prophecy.
At the risk of sounding repetitious, it is important to stress that factual accuracy is not, of itself, a sign of divine source of prophecy (Deut. 13: 1-5). There remain the issues of (1) who God has actually sent, (2) the preservation of the purity and the sanctity of the message, and (3) the delivery to the intended destination.
False Prophecy
To summarise, false prophecy is any purported supernatural message which is not sourced from God, or which requires human mediation for completeness, or which is not delivered in accordance with divine instruction, or which is in any way contrary to the word of God.
Normally, it ought to be that true prophecies will always and only be carried by true prophets of God while false prophecies would be the products reserved for prophets not appointed by God. But due to man's unfaithfulness and God's sovereignty, it so happens that false prophecies may emanate from genuine children of God while God may also route true prophecies through strangers to the household of faith, even including non-moral beings such as donkeys!

