The restraint of the modifications of the mind-stuff is Yoga.
My copy of the Sutras includes commentary from Sri Swami Satchidananda, who writes of this first substantive point:
In this Sutra Patanjali gives the goal of Yoga. For a keen student this one Sutra would be enough because the rest of them only explain this one. If the restraint of the mental modifications is achived one has reached the goal of Yoga. The entire science of Yoga is based on this. Patanjali has given the definition of Yoga and at the same time the practice. "If you can control the rising of the mind into ripples, you will experience Yoga."
I feel a little moved to do commentary-upon-commentary here. We all know that "Yoga" comes from the same word as "yoke," and means something like "to unite," right? What's being united?--well, conventionally, what we call "Self" and "God" (though of course, once the experience of Yoga is underway, there is no separation, so no labels are possible). From there, a key to understanding this passage is to focus on the relative strangeness, or unexpectedness, of that final phrase: you will experience Yoga. This phrase is far different from the more commonly uttered, "Yeah, sometimes I practice (or 'do') Yoga." Everybody knows somebody who does yoga. Only the lucky know someone who has experienced it.
Now, if you don't grasp this second point -- there are something like 50 more of them to work through. So don't miss this! I often find that comparing the "heart" of various mysticisms helps me to see through formal or cultural distinctions that are ultimately only apparent. So look at the quote I posted in my left margin from Parmenides:
Our thought cannot grasp the One as long as any other image remains active in the soul... To this end, you must set free your soul from all outward things and turn wholly within yourself, with no more leaning to what lies outside, and lay your mind bare of ideal forms, as before of the objects of sense, and forget even yourself, and so come within sight of that One.
To my mind, this is a perfect (and not coincidental) description of how to "experience" what Patanjali knows as Yoga. What Patanjali calls "the mindstuff" appears in the excerpt from Parmenides as "active images in the soul" and impressions of "outward things," and even, finally, "yourself." Then, does Parmenides recommend a way to "restrain the modifications of" such mindstuff? Maybe. What does "set free your soul from" mean?--what does it mean to "lay your mind bare" of forms? Or to "forget" yourself? How exactly does that happen?
Parmenides, who is often identified as the "Father of Logic," would be better understood in his role as an Iatromantis (Greek: ἰατρόμαντις). I've mentioned this before, but I want to deal with it again because it's an idea that's very important to my understanding of mysticism & philosophy. In his role as an Iatromantis, Parmenides would usher a "seeker" into a sacred cave, would advise the initiate to lie down, as comfortably as possible (on his back), and then to not move... for three days. The procedure was known as "incubation." Meanwhile, Parmenides would stand at the mouth of the cave as a watchman. Wikipedia wraps this part up for me:
More than just a medical technique, incubation reportedly allowed a human being to experience a fourth state of consciousness different from sleeping, dreaming, or ordinary waking: a state that [Peter] Kingsley describes as “consciousness itself” and likens to the turiya or samādhi of the Indian yogic traditions.
Wow! So this is what "philosophy" was on the eve of Socrates. It's difficult to imagine anything farther removed from what goes on in academic philosophy departments nowadays. Notice that, just like Yoga, Parmenides' philosophy is immersive, physical, and experiential. There is no thinking it, apart from doing it. Notice also that the philosophy of Parmenides, like Yoga, aimed at a very specific end: it is, well, to experience Yoga.
For me, all of this precipitates a thinking about my pedagogy. Can I make my own teaching aim at such heights?--can I find a way to guide students to union with the divine? Or is such an idea too preposterous for the 21st century? Are there protections against this kind of teaching built into bureaucratic systems that regulate university life--? And if I'm being conspiratorial: --on purpose?
If any of you are tempted (oh, I hope you are!), Kingsley's most important book is titled Reality. I long to talk to somebody about it!
P.S. -- there were hints of this much misunderstood/neglected tradition in E.R. Dodds' book, The Greeks and the Irrational, published in 1951. Possibly this was Kingsley's source on Iatromantis?