In the ancient world, most persons believed that dreams were caused by the wandering of the soul while the body was sleeping. The early Christians generally held to the common view of their day.
I will go further and say that the soul does not even fall into sleep along with the body, nor does it even lie down in rest with its companion. For it is agitated in dreams. Tertullian (c. 210, W), 3.558
Where do dreams come from? The fact is, [the soul] cannot rest or be altogether idle, nor does it confine its immortality to the still hours of sleep. Instead, it shows that it possesses a constant motion. It travels over land and sea. It trades. It is excited. It labors. It plays. Tertullian (c. 210, W), 3.222, 223
Indeed, in these dreams, good actions are useless; and crimes are harmless. For we will no more be condemned for imaginary acts of sin, than we will be crowned for imaginary martyrdom. But you will ask, “How can the soul remember its dreams, when it is said to be without any mastery over its own operations?” This memory must be a special gift of the ecstatic condition. Tertullian (c. 210, W), 3.224
Likewise in sleep, revelations are made of high honors and eminent talents. Remedies are also discovered, thefts brought to light, and treasure indicated. Thus Cicero’s eminence was foreseen by his nurse, while he was still a little boy. . . . How many commentators and chroniclers vouch for this phenomenon! Tertullian (c. 210, W), 3.225
Dreams are inflicted on us mainly by demons, although they sometimes turn out to be true and even to be favorable to us. . . . But all those visions that are honest, holy, prophetic, inspired, instructive, and inviting to virtue . . . must be regarded as emanating from God. For He has promised, indeed, to pour out the grace of the Holy Spirit upon all flesh. . . . It was, indeed, by an inspiration from God that Nebuchadnezzar dreamed his dreams. . . . The third class of dreams will consist of those that the soul apparently creates for itself from an intense application to special circumstances. Tertullian (c. 210, W), 3.225, 226
They say that dreams are more sure and clear when they happen towards the end of the night, for then the vigor of the soul emerges and heavy sleep departs. Tertullian (c. 210, W), 3.226
As for those persons who suppose that infants do not dream, . . . they should observe attentively their tremors, nods, and bright smiles as they sleep. From such facts, they should realize that they are the emotions of their soul. Tertullian (c. 210, W), 3.226, 227
In dreams, I am still occupied with what the soul has seen and handled in the day. Gregory Thaumaturgus (c. 238, E), 6.38
It is a matter of belief that in dreams, impressions have been brought before the minds of many. Some relate to divine things; others, to future events of this life. This may be with clearness or in a symbolic manner. Origen (c. 248, E), 4.416