be foolish (Hebrew #3688)

Jeremiah
10:8   But they are altogether
'echad (Hebrew #259)
properly, united, i.e. one; or (as an ordinal) first
KJV usage: a, alike, alone, altogether, and, any(-thing), apiece, a certain, (dai-)ly, each (one), + eleven, every, few, first, + highway, a man, once, one, only, other, some, together,
Pronounce: ekh-awd'
Origin: a numeral from 258
brutish
ba`ar (Hebrew #1197)
to kindle, i.e. consume (by fire or by eating); also (as denominative from 1198) to be(-come) brutish
KJV usage: be brutish, bring (put, take) away, burn, (cause to) eat (up), feed, heat, kindle, set ((on fire)), waste.
Pronounce: baw-ar'
Origin: a primitive root
and foolish
kacal (Hebrew #3688)
properly, to be fat, i.e. (figuratively) silly
KJV usage: be foolish.
Pronounce: kaw-sal'
Origin: a primitive root
: the stock
`ets (Hebrew #6086)
a tree (from its firmness); hence, wood (plural sticks)
KJV usage: + carpenter, gallows, helve, + pine, plank, staff, stalk, stick, stock, timber, tree, wood.
Pronounce: ates
Origin: from 6095
is a doctrine
muwcar (Hebrew #4148)
properly, chastisement; figuratively, reproof, warning or instruction; also restraint
KJV usage: bond, chastening ((-eth)), chastisement, check, correction, discipline, doctrine, instruction, rebuke.
Pronounce: moo-sawr'
Origin: from 3256
of vanities
hebel (Hebrew #1892)
from 1891; emptiness or vanity; figuratively, something transitory and unsatisfactory; often used as an adverb
KJV usage: X altogether, vain, vanity.
Pronounce: heh'bel
Origin: or (rarely in the abs.) habel {hab-ale'}
.