Chapter 56 is blunt,
The idea that speaking not know should reasonably include feeling and thinking. In fact, isn’t speech just giving voice to one’s emotions and thoughts? And for humans, writing is just another form of speech.
Emotion drives thought; thought manipulates emotion 
Seagulls are emotional just like humans. They exhibit anger, fear, need, social bonding, etc. These emotions instigate action in both seagulls and humans. In humans, emotions also instigate and/or influence thought. This is problematic on several levels. Chapter 71 sums up the problem quite literally as, Realizing I don’t’ know is better; not knowing this knowing is disease. Any certainty of belief feeds back into our emotions, amplifies them somewhat which then easily initiates over reactions and stress. It can easily be a vicious circle!
Profound Sameness cripples certainty
One’s awareness of profound sameness within each flowing moment results in Knowing not speak. Conversely, one’s awareness of differences (i.e., names, words) naturally results in the speaking not know. Typically, difference awareness within each moment is a blend of past, present, and future cognitive dynamics. In contrast, the ghostly awareness of profound sameness is by definition inexplicable, i.e., The name possible to express runs counter to the constant name. When profound sameness floods the perception, the past, present and future, blend into an eternal now. Here, knowing can’t speak (think, or write).
I feel that knowing not speak arises from the knowing recognition that speaking easily falls on deaf ears, i.e., we can’t really understand what we don’t already intuitively know. (See We only understand what we already know )
Conversely, it is natural that speaking not know. The deep social element of speech has nothing to do with knowing anything, i.e., people talk, dogs bark, birds chirp. The innate need to communicate—emotion—is what actually drives speech and writing. It’s the urge to help, to tell a story, call out a warning, etc. More deeply, speech and writing may also be an attempt to convince ourselves… a sort of talking to ourselves aloud. So, finally I know why I am actually writing all this!
Emotion runs the show here
Given how thoroughly emotion influences human thought, I refer often to need, fear, emotion, and instinct in a broader sense than usual. I’ll address these briefly…
Need and fear: I use the terms need and fear to convey, in the broadest possible sense, the primal biological driving forces of life. Meaning: Feeling need attracts us to what ostensibly facilitates survival; feeling fear repels us from what ostensibly hinders survival. Such need and fear are often below the threshold of thought. They only evoke conscious thoughts once they pass some relative threshold of awareness.
Emotion: I use the term emotion as broadly as possible to differentiate feeling from thinking. This includes all the experiences, conscious or otherwise, that we are unable to adequately describe through language or portray artistically. Chapter 14 may hint at this subtlety… This is called the without of shape form, the without of matter shape.
Instinct: We commonly think instinct pertains mostly to animals. It is their means of making choices in life. We, on the other hand, believe we have free will, and thus are able to operate outside the bounds of instinct. This is more wishful thinking than actuality. In any case, instinct is something innate and along the lines of need, fear, and emotion. Instinct is the biological bedrock upon which all we perceive originates.
Writing my observations down like this helps me flesh out views that fall outside the mainstream paradigm. Sure, this feels a little unsettling at times. On balance though, seeing life from other angles is healthful, not heretical. I imagine most people would agree, at least until a particular view begins to threaten their own sacred cow. At that point, need, fear, and emotion (instinct) carries the day.