Testing for validity and invalidity

The determination of the truth value of statements it's an easy step to apply that knowledge to the testing of deductive arguments for validity or invalidity. In a validity argument, if all its premises are true then its conclusion must be true; or alternatively, in a valid argument, it is impossible for all its premises to be true and its conclusion false.....

As per; Bruce Waller in his book Critical Thinking.....

elaborate more.u kind left me

elaborate more.u kind left me.
Mkuu in our daily life not all reasonimg are terms to provide conclusive evidenceor reasons for truth of given conclusion,what is done is merely provison of evidence to show that the conclusion we arrive at is well found.That's why my teacher used to say what matters is what you have to prove in the court of law perhaps if the CORAM concurs with it,so bargaining power is an important essential for a lawyer.The evidence provided before the court of law no matter is the truth or lie as long as it proves something accurately then it is valid reasoning.Though it does not happen always.mfano leo mtoto anaweza kubakwa na mtu mwingine kabisaaa ila akashawishiwa na wazazi au ndugu zake kumtaja mtu mwingine kabisa ambaye hausiki na hivyo mahakama itamhold liable mtu huyo since the witness has proved beyond reasonable daught hence that's a valid inference or conclusion thou a good lawyer should not depend on these chances because they rarely happen instead one should cultivate the behavior of scrutinizing facts.In DEDUCTIVE reasoning two premises cannot contrast with each other for it will lead to invalid conclusion.SO JIPANGEEEE