“Remember, though, your best weapon is between your ears and under your scalp—provided it’s loaded.”
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 1, “The Marching Hordes” (p. 14)

Tunnel in the Sky is a juvenile science fiction novel by American writer Robert A. Heinlein, published in 1955 by Scribner's as one of the Heinlein juveniles. The story describes a group of students sent on a survival test to an uninhabited planet, who soon realise they are stranded there. The themes of the work include the difficulties of growing up and the nature of man as a social animal.
“Remember, though, your best weapon is between your ears and under your scalp—provided it’s loaded.”
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 1, “The Marching Hordes” (p. 14)
“The death rate is the same for us as for anybody … one person, one death, sooner or later.”
Robert A. Heinlein book Tunnel in the Sky
Tunnel in the Sky (1955), Captain Helen Walker, Ch. 2
“Man is not a rational animal; he is a rationalizing animal.”
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 2, “The Fifth Way” (p. 42)
“Rod…were you born that stupid? Or did you have to study?”
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 6, “I Think He Is Dead” (p. 104)
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 2, “The Fifth Way” (p. 43)
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 2, “The Fifth Way” (p. 42)
“Good stories are rarely true.”
Robert A. Heinlein book Tunnel in the Sky
Source: Tunnel in the Sky (1955), Chapter 3, "Through the Tunnel"