I would say that the core insight (that I have taken away) from philosophy is that if you start in the middle, you will conclude only whatever assumptions are relatively embedded in the terms of the question that you ask. All interesting philosophical discussions start at a topic, and walk backwards. Forwards just doesn't happen. So...the Cartesian strategy of starting at the beginning has emerged as the only sane one. Let's not give any room to go backwards.
So...a foundationalist inductivist like me suggests that we start at the beginning ... with what we sense...and mvoe forward from there. Any even moderately competent developmental psychologist will point out that we do indeed appear to start from nowhere...There is no CONTENT to our minds at birth (only structure)...indeed, to reference mind at the beginning is a bit much. Instead...we have reflexes, and built-in preferences, and a brain structure that will accumulate information.
In the first few months, an infant functions more or less as a machine...if (unpleasantness) then {cry}. If (pleasure) then {more}. Pleasureable/Painful (good/bad) is the primary awareness of the child. It predates everything else by a LONG time (months). Somewhat after that, by observation, the child develops (by observation) the distinction between self and not-self (things I control, things I don't). Eventually, the child has control of it's own muscles. Later, the notion of the external world as regular arrives (object permanence). Soon thereafter, it moves into the primary animal-kingdom conditioning pattern. If (good response), increase frequency of (prior behavior), but unlike other animals, it also has vocal cords, brain modules designed for language acquisition, and built-in pleasure from communicating
After this, we develop the capability to handle number...Montessori on the process of acquisition of the concept of number permanence is irreplaceable here. Also...it does an awful good job of making one laugh at Pythagoras, Plato, and Bertrand Russell's attempts to argue for number as something beyond inductivist positions.
Long after that...we develop the notion of other perspectives. What I see/believe is not what you see/believe. Piaget did the experiments...it's near 6yo that this ability emerges. Also, we separate the world into intentional and inert sometime early in life (between ~3? and 9).
Being aware that the human brain creates the notion of the not-self (and by contrast the self) sometime after months of observing the world seems to me to be essential to any undestanding of foundational philosophy. The external world is NOT a postulate...it is a conclusion that is the best predictive hypothesis from sense data.
An awful lot of the first categories that we learn as human beings are things. Mama. Dada. Dog. Appuh. 'Puter. An awful lot of what we do when learning concepts is observe things in the world...hear a (new) word used to describe a thing...and then create a mental (fuzzy) circle separating "things like that" from "things not like that". However, that's not all of learning, that's mostly learning of nouns, and some other parts of speech. A different huge amount of child-word-acquisition is "If I say X, I get results Y"...and calculating based on X=>Y.
Also...early on (3?) a preliminary forms of ethics evolves in the human child. Early ethics ~= Justice: To each what they deserve. Nice people deserve good stuff. Mean folks should be punished.
Most of the rest of child ethics is a result of predictive adult-management. If I say "God is good," or "Save the environment", I get praise from parent...so do. The statements are moderately content-free when said for the first 100 times. The insidiousness of this is that phrases are being attached to a child's emotional substrate at a point prior to the child's ability to even identify whether the phrases have meaning. Only folks who are aspie-ish will ever go back and screw with this conditioning.
Sometime near 14 (minus, say, 1 -1.5 years per sigma), the mind matures further, and becomes capable of handling abstraction in a decent way....now that the foundational stuff of having constructed an internal set of tags associating words with things is handled. Of course, also in the same time frame, hormones flood our bodies, and our ability to focus on non-sexual stuff drops remarkably for ~4 years.
ASIDE: this gives notably advanced kids, or hormonally delayed kids an enormous advantage that I've not head discussed previously: their primary abstract learning years (10-14) occur in a relatively hormone-free environment. Further, given that girls hit the hormones earlier...does that damage their chance to learn abstractly? Also, Blacks have earlier sexual maturity. This may cause issues given hormones. Does this imply that single-sex schools are more important for girls and blacks than for whites, asians, and boys. Or does the age of abstraction drop as well? Normal folks hit the age of mental abstraction roughly at the age they lose the interest in making mental abstractions.
So...when we reach the age of intellectual maturity (20?)...our brains are roughly adult brains...however most philosophers approaching questions here have forgotten that most (all?) of our CONCEPTS are "tap-it" concepts, with the concept itself having been created from experience...and that many of our WORDS are effect-based words, not words with referents.
As a foundationalist...it is my intent to attach meaning to words by reference to referents in the world that I can tap (cat), point-to (there is obviously some emotion being experienced by 2 people who cannot seem to keep their hands off one another -- Since people are all ~the same...that emotion [as said by a 10yo]), reference by date (Remember what I felt like that day when...). Mostly, this is because otherwise...I don't know WTF you're talking about...and I assert that most likely neither do you.
Mostly, I don't believe that people are doing more than mouthing desires when they talk about stuff that they can't take back to taps.