Android Studio - Material Design Problem

Hallo!

Ich habe jetzt in der styles.xml das Design auf "Material Design" geändert.
Wenn ich jetzt meine App aber ausführe, stoppt sie sofort.
Was könnte das Problem sein?

LogCat
12-04 12:34:02.180 5074-5074/? I/zygote: Not late-enabling -Xcheck:jni (already on)
12-04 12:34:02.205 5074-5074/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
12-04 12:34:02.682 5074-5074/ga.code.android_quiz I/InstantRun: starting instant run server: is main process
12-04 12:34:02.963 5074-5074/ga.code.android_quiz D/AndroidRuntime: Shutting down VM
12-04 12:34:02.975 5074-5074/ga.code.android_quiz E/AndroidRuntime: FATAL EXCEPTION: main
Process: ga.code.android_quiz, PID: 5074
java.lang.RuntimeException: Unable to start activity ComponentInfo{ga.code.android_quiz/ga.code.splashscreen.HomeActivity}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
at android.support.v7.app.AppCompatDelegateImplV9.createSubDecor(AppCompatDelegateImplV9.java:356)
at android.support.v7.app.AppCompatDelegateImplV9.ensureSubDecor(AppCompatDelegateImplV9.java:325)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:286)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
at ga.code.splashscreen.HomeActivity.onCreate(HomeActivity.java:17)
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
at android.app.ActivityThread.-wrap11(Unknown Source:0) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
at android.os.Handler.dispatchMessage(Handler.java:105) 
at android.os.Looper.loop(Looper.java:164) 
at android.app.ActivityThread.main(ActivityThread.java:6541) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)