1.7 Correct knowledge is direct, inferred or proven as factual
Of these five, there are three ways of gaining correct knowledge 1) perception, 2) inference, and 3) testimony or verbal communication from others who have knowledge.
So this is talking about 1.6, about how there are five types of thoughts, and the first one is correct knowledge. The first way of obtaining correct knowledge (by which I mean knowledge which is true) is through direct perception. Iyengar states that initially our perceptions should be checked with logic and then to see if it corresponds with traditional wisdom. He also says that practicing yoga asanas, brings intelligence to the surface, which then sharpens our ability to discriminate between our perceptions. I suppose this happens through being more aware of the body during asana practice, through being conscious of the balances and imbalances throughout the body, this in turn allows for the quietening of the mind.
I like the way that this sutra seems to value direct experience over hearing something, even if it is from an expert. This fits with my own personal view of the world, which is largely influenced by Zen Buddhism. I like the way in Zen that there are few things to ‘believe’, if any, it is all to do with your own direct experience. I struggle when belief systems or religions require people to ‘believe’ things, to take them at face value, rather than to experience things for themselves and then make their own minds up. I suppose these religions could be said to be forming the ‘testimony of experts’ part of this sutra, but it seems to me that these three ways of forming correct knowledge should fit together, rather than just follow something in blind faith without any direct experience or reasoning. True knowledge should fit with your direct experience, your reasoning and what experts say.