This is an interesting antithesis to Descartes' cogito ergo sum: instead of the "I" reassuring itself on the thought of a thinking being, thought arises from the assurance of the "I".
What Helen Keller seems to describe is more akin to Lacan's 'pure life' or Hegel's sinnliche Gewissheit (sense-certainty) as kind of primordial basis for what leverages with consciousness (however, much like with Decartes' ego, this is really a retroactive reference).