One of the most trouble-making aspects of ignorance is grasping at what ‘is’ true. We think there is a truth independent of what we think, and therefore when we choose to try think/believe certain things that are different than what we grasp at being true, our thinking/believing lacks any power and seems like make believe. I can think X, but I know it is not true, so it doesn’t move my mind any. Virtually every Dharma mind involves believing in certain things, and so this ignorance can block us from developing virtually every Dharma mind.
But with all the objects of Dharma, it is our believing in them that they in fact become true – believing makes them true. This is especially true with Tantric objects. The key point is wherever you imagine a Buddha, a Buddha actually goes. So if I believe something is an emanation of my spiritual guide, he enters into that object completely and inseparably, and it becomes actually true – the object becomes an emanation of my spiritual guide and I can receive his blessings through it. In this way, if I believe that all objects are his emanations and that I am in the pure land (the pure land is a world emanated by him for practitioners to complete their training), then this becomes true – I actually am in the pure land. So it is a correct belief – a belief in something that is true. When I understand this, then the belief has real power to move my mind and oppose my delusions.
There is a deeper level at which believing makes things true. The mental action of believing in an object of a correct belief plants the karma on your mind which will ripen in the future in the form of that object appearing directly to your mind as your living reality. In other words, by engaging in the mental actions of pure conceptions, we create the karma to have pure appearances later. When we have pure appearances, it is easy to have pure conceptions about them, and so the karmic cycle becomes self-replicating.
To be precise with all of this, because Buddha’s mind pervades everywhere and is the ultimate nature of all things, whether I personally believe it or not does not make it true since it is already true (from the perspective of the Buddha’s mind). But my ignorance obscures my mind from this truth. But by believing it to be true, then it makes this truth become manifest within my mind (before it was a hidden truth) and then it functions within my mind as being a manifest truth.